Our workshop builds on last year’s successful event at NJIT, which contributed to the research roadmap for Altermagnetism.  This year, we aim to unite leading theorists and experimentalists in the field, with a primary focus on bridging these two essential research directions. The program will emphasize practical connections between theory and experiment. Theoretical presentations will highlight measurable effects and experimental validation, while experimental findings will be contextualized within current theoretical frameworks and predictions. We strongly encourage participation from both established experts and early-career researchers. 

OUR WORKSHOP  is SUCCESSFULLY COMPLETED

We hope to see each other next year

The group photo is below

USEFUL LINKS to PROGRAMS and DATABASES that help with AM MATERIALLS IDENTIFICATION and SYMMETRY ANALYSIS:

Smolyanyuk, Šmejkal, and Mazin,  AMCHECK:  https://github.com/amchecker/amcheck

TALKS and POSTERS

WORKSHOP LOCATION:  

Agile Lab L70 room in the Central Kings Building on NJIT Campus. 

Workshop Chair: Andrei Sirenko, NJIT

REGISTRATION  FEE:

zero for registered participants. No last min walk in because of the limited room capacity

SCIENTIFIC COMMITTEE: 

Igor Mazin (George Mason U.), Jeroen van den Brink ( Leibniz Inst. for SSM Research, IFW Dresden), and Sang-Wook Cheong (Rutgers U.)

LOCAL ORGANIZERS

Junjie Yang, Trevor Tyson, and Andrei Sirenko, all from NJIT

INVITED SPEAKERS for 2026 WORKSHOP

Libor Šmejkal MPI Dresden  (Plenary talk)

Badih Assaf, Notre Dame U.

Daniel Agterberg, University of Wisconsin

Turan Birol, U. Minnesota

Jeroen van den Brink, Leibniz Inst. for SSM Research, IFW Dresden

Kenneth Burch, Boston College

Jennifer Cano, Stony Brook U.

Sang-Wook Cheong, Rutgers U.

Joachim  Deisenhofer, U. Augsburg

Rafael Fernandes, U. Illinois

Marcel Franz, UBC

John Freeland, APS

Raphael Hermann, Oak Ridge

D-J. Huang, NSRRC, Taiwan

Bharat Jalan, U. Minnesota

Jeroen van den Brink, IFW Dresden

Maxim Khodas, The Racah Inst. of Physics

Junwei Liu, Hong Kong U. of Science and Tech.

Takatsugu Masuda, University of Tokyo 

Emilia Morosan, Rice U.

Madhav Neupane, U. Cent. FL

Karen Rabe, Rutgers,U.

Jennifer Sears, BNL

Alessandro Stroppa, CNR-SPIN, c/o Depart. of Phys. & Chem. Sci., University of L’Aquila

Alberto de la Torre, Northeastern U.

Maximilian Ünzelmann, U. Wuerzburg

David Vanderbilt, Rutgers U.

Jorn Venderbos, Drexel U.

Liang Wu, UPenn

Jing Xia, UC Irvine

Suyang Xu, Harvard University

Pu Yu, Tsinghua University, China

Igor Zaliznyak, BNL

Liuyan Zhao, U. Michigan

Tong Zhou, Eastern Institute of Technology, Ningbo 

Igor Zutic, SUNY Buffalo

LINK to the FIRST WORKSHOP in January 2025

https://sites.google.com/njit.edu/altermagnetism2025/home

TIMETABLE for the 2nd WORKSHOP on ALTERMAGNETISM, Jan 14th  - Jan 16th, 2026

PROGRAM  for the 2nd WORKSHOP on ALTERMAGNETISM, Jan 14th  - Jan 16th, 2026

All Invited talks are 30 min long including questions

ASTRACTS   Jan 14th - Jan 16th, 2026

Wednesday, January 14th, 2026

WE.1 PLENARY SESSION   8:30-9:30   Chair: Igor Mazin (George Mason U.)

WE.1P  Altermagnetism, Antialtermagnetism, and Spin Symmetries

L. Šmejkal1,2,3

1Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany

2Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany

3Institute of Physics, Czech Academy of Sciences, 162 00 Praha 6, Czech Republic

E-mail: lsmejkal@pks.mpg.de

We will introduce the theoretical framework of spin group theory [1–2], which has recently enabled symmetry-based prediction and classification of two distinct families of unconventional magnets: altermagnets exhibit time-reversal broken even-parity (d-, g-, or i-wave) spin-polarized order [1,3], whereas antialtermagnets host time-reversal symmetric odd-parity (p-, f-, or h-wave) spin order [4,5].

We will then summarize recent experimental observations of altermagnetism guided by our theoretical predictions [1–3]. We will focus on momentum-space photoemission spectroscopy of both nonrelativistic and relativistic altermagnetic spin splitting, spin polarization, and chiral magnons, as well as real-space x-ray magnetic circular dichroism spectroscopy mapping of the altermagnetic domains [6]. We will also discuss the crystal anomalous Hall effect [3,7]—an unusual magnetotransport phenomenon that originally motivated the development of spin group theory delimitation of altermagnets and has now been confirmed experimentally in multiple material platforms [7].

In the final part of the talk, we will highlight emerging research directions at the intersection of spintronics, multiferroics, and topological materials, all driven by spin-symmetry concepts. These include large tunneling magnetoresistance and current-induced spin polarization in altermagnets [8]; the altermagnetoelectric effect in altermagnetic multiferroics [9]; and topological quasiparticles in altermagnets and antiferromagnets, along with their impact on enhancing the spin Hall effect [2,10].

[1] L. Šmejkal, J. Sinova, T. Jungwirth, Phys. Rev. X 12, 031042 (2022), Phys. Rev. X 12, 040501 (2022).

[2] V. Mendoza-Estrada et al., Phys. Rev. B 111, 085147 (2025), T. Jungwirth et al., arXiv:2506.22860, Nature, in press (2025), A. Smolyanyuk et al., SciPost Physics Code, 030

[3] L. Šmejkal et al., Science Adv. 6, 23 (2020), Phys. Rev. Lett. 131, 256703 (2023), I.I.Mazin et al., PNAS 118 42 (2021)

[4] A. Birk Hellenes et al., arXiv:2309.01607v3 (2024), A. Chakraborty et al., Nature Commun. 16 (1), 7270 (2025), N. A. Alvarez Pari et al., Phys. Rev. B 112, 024404 (2025).

[5] T. Jungwirth et al., Newton 1, 6, 100162 (2025).

[6] J. Krempasky, L. Šmejkal et al., Nature 626, 517 (2024), S. Lee et al., Phys. Rev. Lett. 132 (3), 036702, O. Amin et al., Nature 636, 348 (2024), A. Dal Din, L. Šmejkal et al., arXiv:2511.01690 (2025).

[7] H. Reichlova et al., Nature Comm. 15, 4961 (2024), L. Šmejkal et al., Nature Reviews Materials 7, 482 (2022), A. Badura et al., Nature Comm. 16 (1), 7111 (2025).

[8] L. Šmejkal et al., Phys. Rev. X 12, 011028 (2022), L. Golub et al., arXiv:2503.12203 (2025), T. Jungwirth et al., arXiv:2508.09748 (2025).

[9] L. Šmejkal, arXiv:2411.19928 (2024), S. Kim et al. Adv. Sci. 11 (6), 2307306 (2023).

[10] I.I. Mazin et al., arXiv:2309.02355 (2023).

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WE.2 Symmetry & Models  10:00 – noon Chair:  Jeroen van den Brink (Leibniz Inst. for SSM Research, IFW Dresden, Germany)

WE2.1  What do minimal models tell us about non-relativistic spin-splittings

D. F. Agterberg

University of Wisconsin, United States

Altermagnets and odd-parity magnets have recently emerged as important classes of magnetic materials for spintronics due to their vanishing net magnetization and large, strongly momentum dependent, energy splittings between opposite spin electronic states.   Here I present recent progress [1,2,3,4] on developing Hubbard Hamiltonians for altermagnets and odd-parity magnets. These Hubbard Hamiltonians provide microscopic descriptions for p-wave, d-wave, f-wave, g-wave, h-wave, and i-wave non-relativistic spin splittings. Using these Hubbard Hamiltonians, we provide insight into the microscopic origin of the electronic spin-textures, the response properties of these magnetic states, and their interplay with superconductivity.
[1] Minimal models for altermagnetism, M. Roig, A. Kreisel, Y. Yu, B. M. Andersen, and D. F. Agterberg, Phys. Rev. B 110, 144412 (2024).
[2] Altermagnetism from coincident Van Hove singularities: application to κ-Cl, Y. Yu, H.G. Suh, M. Roig, and D.F. Agterberg, Nature Communications 16, 2950 (2025). 

[3] Quasi-symmetry constrained spin ferromagnetism in altermagnets, M. Roig, Y. Yu, R. C. Ekman, A. Kreisel, B.M. Andersen, D.F. Agterberg, Phys. Rev. Lett. 135, 016703  (2025).
[4] Odd-parity magnetism driven by antiferromagnetic exchange, Y. Yu, M.B. Lyngby, T. Shishidou, M. Roig, A. Kreisel, M.  Weinert, B. M. Andersen, D. F. Agterberg, Phys. Rev. Lett. 135, 046701 (2025).

WE2.2  Super-Altermagnetism

Sang-Wook Cheong

 Rutgers University, United States

Altermagnetism is a theoretically proposed class of magnetic states characterized by collinear antiferromagnetic spins combined with alternating local structural environments, arranged so that the symmetry permits ferromagnet-like behaviors—such as spin-split electronic bands—even in the absence of spin-orbit coupling (SOC)¹². To facilitate experimental studies, we define altermagnets more broadly: as spin-compensated magnets with broken combined parity and time-reversal (PT) symmetry, allowing spin-split bands, at least, in the presence of SOC. These altermagnets can be categorized into four types:

M-type: with a net orbital “M”agnetization (analogous to compensated ferrimagnets),

S-type: showing “S”ymmetric spin splitting due to broken time-reversal symmetry (T),

A-type: exhibiting “A”ntisymmetric spin splitting due to broken spatial inversion (P),

S/A-type: displaying both symmetric and antisymmetric spin splitting.

We can also examine spin splitting in the absence of SOC by invoking spin-rotation symmetry rather than using full spin group theory. Altermagnets that exhibit spin splitting without SOC are referred to as strong altermagnets.

In M-type altermagnets, the net magnetization (M) typically arises from SOC and may be small. However, external magnetic fields can flip M, switching the entire Néel vector. The dynamics of these systems are governed by the Néel vector and can operate at THz frequencies. In certain M-type altermagnets, the M direction aligns with the non-relativistic spin splitting direction. This alignment enables the non-relativistic spin splitting to influence properties such as the anomalous Hall effect, anomalous Nernst effect, magneto-optical Kerr effect, and Faraday effect. These particularly responsive M-type altermagnets are termed super-strong M-type altermagnets, or simply super-altermagnets.  We will discuss various material realizations of super-altermagnetism and their versatile functionalities. Super-altermagnetism offers exciting new frontiers in both fundamental science and technological applications.

1. Anomalous Hall effect arising from noncollinear antiferromagnetism, H. Chen, Q. Niu, & A. H. Macdonald, Phys. Rev. Lett. 112, 017205 (2014).

2. Emerging research landscape of altermagnetism, L. Šmejkal, J. Sinova, & T. Jungwirth, Phys. Rev. X 12, 040501 (2022).

3. Altermagnetism with Non-collinear Spins, SWC and Fei-Ting Huang, npj Quantum Materials 9, 13 (2024).

4. Emergent Phenomena with Broken Parity-Time Symmetry: Odd-order vs. Even-order Effects, SWC and Fei-Ting Huang, Phys. Rev. B 109, 104413 (2024).

5. Altermagnetism Classification, SWC, npj Quantum Materials 10, 38 (2025).

6. Electrical switching of a p-wave magnet, Qian Song, - - -, S.-W.Cheong, Nature 642, 8066 (2025).

7. Kinetomagnetism and Altermagnetism, Fei-Ting Huang, and SWC, arXiv:2503.16277 

WE2.3  Spin splitting and symmetry breaking in the band structures of altermagnets

Andrea Urru, Yujia Teng, Mesfin Eshete, Daniel Seleznev, Sebastian Reyes-Lillo, Se Young Park and Karin M. Rabe

Department of Physics & Astronomy, Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, United States

Altermagnetically ordered crystals exhibit characteristic patterns of spin splitting in the one-electron bandstructure. In a first-principles study of altermagnetic spin splitting in G-type antiferromagnetic ferroelectric BiFeO3, we developed two approaches to display the spin splitting [1]. One is a bandstructure plot that samples the general k-points, rather than high-symmetry points and lines, to provide an accurate representation of spin splitting throughout the Brillouin zone. The other is the parametrization of the spin-splitting function using a symmetry-adapted basis set of Brillouin zone functions, and study of the associated nodal surfaces. Both of these approaches involve the identification of the symmetries in the system. Here, we extend the discussion to systems where the lower-symmetry altermagnetic crystal is related to a higher-symmetry magnetic crystal by symmetry-breaking modulations such as structural distortions. Systems of interest include ferroelectric altermagnets and altermagnets in which the spin splitting is switchable by an applied macroscopic field or stress.

[1] Andrea Urru, Daniel Seleznev, Yujia Teng, Se Young Park, Sebastian Reyes-Lillo and Karin M. Rabe, “𝐺-type antiferromagnetic BiFeO3 is a multiferroic 𝑔-wave altermagnet,” Phys. Rev. B 112, 104411(2025).

WE2.4  Toward a general symmetry and response tensor-based screening of magnetic point groups

David Vanderbilt,1 Andrea Urru,1 and Turan Birol2

1 Department of Physics and Astronomy, Rutgers University

Piscataway, New Jersey, United States

2 Department of Chem. Engineering and Materials Science, U. of Minnesota Minneapolis, Minnesota, United States

In condensed matter physics, we are often interested in identifying candidate materials that exhibit specific phenomena or effects. To do so, it is crucial to understand the symmetry requirements that permit these effects to arise. Ideally, one would have a tool capable of screening all magnetic point groups (MPGs) and identifying those whose symmetry operations satisfy the necessary conditions and/or allow the specific response tensors of interest. In this talk, we present an open-source Python implementation of such a tool. It has been developed for ordinary magnetic point groups, so that in the context of altermagnetism, it applies to the actual crystal after spin-orbit coupling is included. Our approach largely follows the spirit of the TENSOR and MTENSOR utilities of the Bilbao Crystallographic Server,1,2 but is an entirely independent implementation. Our code allows rapid scanning through all MPGs to search for combinations of allowed responses, and querying of high-order responses as described by its Jahn symbol.3 It also allows for the generation of a handy “MPG Spreadsheet” in Excel format, which can easily be used to screen and sort based on rows (MPGs) or columns (responses). Connections to some published classifications of altermagnets will be discussed.

1. S. V. Gallego, J. Etxebarria, L. Elcoro, E. S. Tasci, and J. M. Perez-Mato, Automatic calculation of symmetry-adapted tensors in magnetic and non-magnetic materials: a new tool of the Bilbao Crystallographic Server, Acta Cryst. A 75, 438 (2019).

2. M. I. Aroyo, J. M. Perez-Mato, D. Orobengoa, E. Tasci, G. De la Flor, and A. Kirov, Crystallography online: Bilbao Crystallographic Server, Bulg. Chem. Commun. 43, 183 (2011).

3. H. A. Jahn, Acta Cryst. 2, 30 (1949).

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WE.3 Inelastic Neutron Scattering   13:00 – 15:00 Chair:  John Tranquada  (Brookhaven National Lab.)

WE.3.1   Inelastic neutron scattering in MnTe

Raphael Hermann and George Yumnam

Materials Science and Technology Division, Oak Ridge National Laboratory, United States

Altermagnets represent an emerging paradigm in magnetism, combining zero net magnetization with broken Kramers degeneracy and thereby allowing anomalous Hall effects without macroscopic stray fields. Hexagonal MnTe is an established d-wave altermagnet that also exhibits strong magnon and paramagnon carrier-drag effects, making it a compelling platform for probing links between microscopic spin dynamics and unconventional transport. We present time-of-flight inelastic neutron scattering measurements on single-crystal MnTe performed on the SEQUOIA spectrometer at SNS, complemented by triple-axis measurements on the HB-3 spectrometer at HFIR. These measurements provide momentum- and energy-resolved spectra of the magnon branches and reveal features consistent with the chiral splitting predicted by Smejkal et al. (Phys. Rev.X 12, 4 (2022)) and reported by Liu et al. (Phys. Rev. Lett. 133, 156702 (2024)). We will discuss the robustness of these observations with respect to sample size and quality, and possible artifacts.

We acknowledge collaboration with Jiaqiang Yan, Matthew Stone, and Songxue Chi. Work supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division,

hermannrp@ornl.gov

WE.3.2    Recent Update of Neutron Scattering Study on Altermagnet MnTe

Takatsugu Masuda

Institute for Solid State Physics, the University of Tokyo

We reported inelastic neutron scattering (INS) experiments on single crystals of the altermagnetic candidate MnTe by using HRC spectrometer at J-PARC [1]. Well-defined magnon excitations were observed at T = 10 K. An unconventional splitting of magnon dispersions is clearly observed in the spectrum. The -wave harmonic symmetry of altermagnetism in MnTe is verified in the constant-energy slice. Both the split dispersions and -wave patterns are well reproduced by the linear spin-wave theory (LSWT) calculation considering a Heisenberg spin Hamiltonian with a pair of alternating exchange interactions. The calculated neutron chiral factor further demonstrates the chiral splitting of the magnon dispersions. Our results confirmed altermagnetism from the perspective of spin excitation and highlighted its non-relativistic exchange origin, establishing a firm foundation for future explorations in this new magnetic ground state. In this workshop, I will talk the recent update of neutron scattering study on MnTe.

[1] Z. Liu et al., Phys. Rev. Lett. 133, 156702 (2024).

WE.3.3 Magnon characterization in altermagnetic FeF2

J. Sears,1 I. A. Zaliznyak, V. O. Garlea, D. Lederman, J. M. Tranquada

1 Brookhaven National Laboratory, United States

The rutile structure material FeF2 is a well-known classical antiferromagnet which has recently been reexamined in the context of altermagnetism. While the material is highly insulating and not amenable to electronic band structure measurements, altermagnetism can also manifest as a characteristic splitting in the magnon bands. We present inelastic magnetic neutron scattering measurements characterizing the energy, momentum and polarization dependence of magnons in FeF2. These high-resolution measurements allow us to examine the effects of altermagnetic interactions on the energy and polarization of the magnetic excitations in this material.

Work at Brookhaven is supported by the Office of Basic Energy Sciences, Materials Sciences and Engineering Division, U.S. Department of Energy under Contract No. DE-SC0012704.

WE.3.4    Emerging magnetism in candidate altermagnet Fe1-xCrxSb2

I. A. Zaliznyak

 Brookhaven National Laboratory, United States

The system Fe1-xCrxSb2 presents an interesting opportunity for progress in understanding altermagnetism in systems with itinerant electrons.  The x = 0 parent material is diamagnetic, with temperature-induced paramagnetism [1,2], while antiferromagnetic order at temperatures below 275 K is found at x = 1 [2]. Bulk measurements show that magnetism emerges at x > ~ 0.2-0.25 [3]. It has recently been theoretically predicted that for doping near x=0.25, the Fe1-xCrxSb2 marcasite structure, among other non-Bravais lattices with low crystal unit cell symmetry hosts altermagnetic state [4]. Motivated by these predictions, we have carried out inelastic neutron scattering measurements of magnetic excitations in Fe1-xCrxSb2 (x=0.25 and 0.5). In our experiments, we observe a weak, diffuse inelastic signal characteristic of nearly critical magnetic state. The observed excitation reveals an interesting dispersion, which at low energy is concentrated around zero wave vector and is therefore not inconsistent with the expectations for altermagnetism. Additionally, magnetic intensity pattern breaks lattice translational symmetry, perhaps indicating non-trivial topological nature. However, the doping dependence shows similar dynamics in x=0.25 and x=0.5 systems, which becomes stronger on increasing doping, x, while according to LDA calculations altermagnetism is not expected at x=0.5. These observations present interesting challenges to comprehend.

[1] R. Hu, V. F. Mitrovic, C. Petrovic. Phys. Rev. B 76, 115105 (2007).

[2] I. A. Zaliznyak et al., Phys. Rev. B 83, 184414 (2011).

[3] M. B. Stone et al., Phys. Rev. Lett. 108, 167202 (2012).

[4] I. I. Mazin et al. PNAS 118(42), e2108924118 (2021).

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WE.4 ARPES, Films & Surfaces    15:30 – 17:00  Chair:   Joachim Deisenhofer (U. Augsburg, Germany)

WE.4.1 Observation of Altermagnetic Spin-Splitting in an Intercalated Transition Metal Dichalcogenide

Madhab Neupane1, Milo Sprague1, Mazharul Islam Mondal1, Anup Pradhan Sakhya1, Resham Babu Regmi 2, 3, Surasree Sadhukhan 4, 5, Arun K. Kumay1, Himanshu Sheokand1, Igor I. Mazin4 5, and Nirmal J. Ghimire 2, 3

1Department of Physics, University of Central Florida, Orlando, Florida 32816, US

2Department of Physics and Astronomy, University of Notre Dame, Notre Dame, IN 46556, USA

3Stavropoulos Center for Complex Quantum Matter, University of Notre Dame, Notre Dame, IN 46556, USA

4Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030, USA

5Quantum Science and Engineering Center, George Mason University, Fairfax, VA 22030, USA

Altermagnetism is a novel magnetic phase combining characteristics of both antiferromagnetism and ferromagnetic ordering. Despite growing theoretical interest in altermagnetic materials, reports of experimentally verified high-Neel temperature layered compounds are limited or remain to be firmly established. Here, we present an angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) study of Co1/4TaSe2, a compound we identify as a layered altermagnetic material. Magnetic susceptibility measurements confirm type-A antiferromagnetic ordering with a Neel temperature of 178 K. Our ARPES measurements reveal an electronic band structure in excellent agreement with DFT calculations, demonstrating clear signatures of altermagnetic spin splitting at the Fermi surface. Furthermore, temperature-dependent ARPES reveals a reconstructed valence band structure, with observable band shifts and the closing of energy gaps upon heating above the Neel temperature (TN), consistent with the suppression of altermagnetic order. These findings establish Co1/4TaSe2 as a promising platform for exploring altermagnetic phenomena.

WE.4.2 Growth and spectroscopy of altermagnetic MnTe films

Maximilian Ünzelmann, Marco Dittarr,  Lena Hirnet, Hannes Haberkamm, and Friedrich Reinert Universität Würzburg and Würzburg-Dresden Cluster of Excellence ctd.qmat, Germany

Manganese telluride (MnTe) in its hexagonal crystal structure has evolved as one of the workhorse materials for realizing altermagnetic band structures with sizable momentum-dependent spin splitting. In addition to bulk single crystals the synthesis of MnTe thin films represents an important topic in this field, given the advantages of, e.g., growing the material on functional substrates and building heterostructures to create internal interfaces not present in the bulk. Here we report on the growth and spectroscopy of epitaxial MnTe thin films whose atomic and electronic structure is studied by x-ray and electron diffraction as well as angle-resolved photoemission spectroscopy (ARPES). We grow high-quality films on various substrates ranging from transparent band insulators to topological insulators and metallic transition metal chalcogenides. While the former will be useful for transport experiments or optical spectroscopy, the latter two host topological surface states that may trigger interface effects in particular the interplay of spin-polarized topological boundary modes with altermagnetic bands. Furthermore, metallic substrates are highly relevant to avoid charging the insulating MnTe films in high-resolution electron spectroscopy measurements such as ARPES. We discuss the formation of superstructures on the MnTe(0001) surfaces – which may be of interest to address the almost unexplored field of surface effects in MnTe – and, finally, we present how circular dichroism in resonant x-ray photoelectron diffraction allows to address the altermagnetic sublattice structure beyond the level of band structure.

WE.4.3  Chiral superlattice-induced spin-polarized current from collinear antiferromagnet

Suyang Xu

Department of Chemistry and Chemical Biology, Harvard University, United States

We report our surprising observation that a natural chiral superlattice can induce spin-polarized current from the collinear antiferromagnet (AFM) UOTe, despite near-zero magnetization. Using TEM, we identify a long-range planar chiral superlattice in UOTe, which can be viewed as frozen chiral phonons at finite wave vector. We further observe chiral domains by optical circular dichroism. UOTe without chiral superlattice is a conventional collinear AFM without spin-polarized current or Berry curvature. However, the chiral superlattice couples strongly to itinerant Dirac electron spins in the collinear AFM, inducing a sizable spin-polarized current. Furthermore, the chiral superlattice modifies the quantum geometry, inducing total Berry curvature abruptly near Neel temperature, generating an anomalous Hall angle ~0.14, among the largest in bulk magnets. Theoretically, UOTe's PT-symmetric Dirac fermion acts as a singularity, generating strong low-energy responses under weak PT breaking by the chiral superlattice. Our result points to a new chiral superlattice path towards functionalizing AFMs, both statically and dynamically. More broadly, our study bridges chirality, superlattices and unconventional magnetism.

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WE.5 ROUND TABLE DISCUSSION     17:00 – 18:00

Moderator(s): Igor Mazin (George Mason U.)

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Thursday, January 15th, 2026

TH.1 XRAYs   Chair: Valery Kiryukhin (Rutgers U.)  8:00  - 10:00

TH.1.1    What Can Polarized X-rays Tell Us About Altermagnets?

John W. Freeland

Advanced Photon Source, Argonne National Laboratory, United States

Polarized X-ray spectroscopy and scattering have for several decades been powerful tools to explore the element resolved nature of magnetism in solids. With the recent emergence of the field of altermagnetism, it raises the question of how to uniquely distinguish between a simple antiferromagnetic and altermagnetic order.  Recent work with polarized spectroscopies suggests the possibility to fingerprint the altermagnetic groundstate. Here, I will review these types of X-ray probes and share some ideas these results and other avenues to explore features of the altermagnetic ground state.

TH.1.2   Symmetry control of the anomalous Hall effect in altermagnetic α-MnTe

Alberto De la Torre Duran

Northeastern University, Burlington, Massachusetts, United States

Altermagnetism is a recently identified magnetic phase that unites the spin-polarized electronic bands of ferromagnets with the compensated magnetic order of antiferromagnets via unconventional symmetry operations. Controlling the Anomalous Hall Effect in altermagnets is fundamental for spintronic devices. In strained MnTe/GaAs films, the magnitude and polarity of the AHE were unexpectedly tuned by field-cooling (FC). Here, we present a combined X-ray magnetic circular dichroism (XMCD), circular dichroism resonant inelastic X-ray scattering (CD-RIXS), photoemission, and Raman study in thin films of the altermagnetic α-MnTe [1]. Our combined spectroscopy study reveals a symmetry reduction in MnTe/GaAs, allowing a non-zero Dzyaloshinskii–Moriya interaction while maintaining the spin-split electronic and magnetic structure. We interpret the tunability of the AHE in terms of a novel term in the Landau theory enabled by magnetostriction. Altogether, our data demonstrates that substrate strain and symmetry engineering open a pathway toward next generation magnonic and spintronic devices based on altermagnets.

[1] S. Bey et al., arXiv:2409.04567 (2024)

TH.1.3 Bi-altermagnetism unveiled by sublattice-specific circular dichroism in resonant inelastic X-ray scattering

Di-Jing Huang

National Synchrotron Radiation Research Center, Taiwan

An altermagnet is a recently identified class of magnets that exhibit a zero net magnetic moment but break symmetry under the combined operations of parity and time reversal. It typically consists of two magnetic sites of opposite spins related by rotation within the unit cell. Here, we use circular dichroism (CD) in resonant inelastic X-ray scattering (RIXS) to identify a new form of altermagnetism, namely bi-altermagnetism, in the correlated insulator Fe2Mo3O8, which comprises two altermagnetic sublattices: one with alternating quasi-octahedral Fe environments and the other with alternating tetrahedral Fe environments. We experimentally revealed the emergence of CD in an achiral, zero-magnetization system, thereby probing mirror-symmetry breaking associated with altermagnetic order. Notably, the CD appeared at sublattice-specific excitations of the octahedral and tetrahedral sites, indicating symmetry breaking in both altermagnetic sublattices. Calculations based on a model with the bi-altermagnetic order along the c axis successfully reproduce the observed CD. Our findings provide compelling evidence for bi-altermagnetism in Fe2Mo3O8, and showcase the use of RIXS-CD as a probe of magnetic sublattices in systems with zero net magnetization.

e-mail: djhuang@nsrrc.org.tw

TH.1.4 Emerging Altermagnetism and Polar States in Strained Metallic RuO2 Films

Bharat Jalan

Department of Chemical Engineering and Materials Science, University of Minnesota, Twin Cities, United States

RuO2, a rutile 4d-transition metal oxide, exhibits a unique crystal structure with both edge- and corner-sharing octahedra. This intrinsic anisotropy, when combined with strain engineering, provides a powerful avenue for tuning anisotropic electronic and optical properties. However, from a synthesis perspective, challenges such as variable Ru valence states, Ru/O stoichiometry control, anisotropic strain states, and structural defects can make it difficult to distinguish intrinsic properties from extrinsic effects in RuO2 thin films – a classic trick in the pursuit of novel functionalities in quantum materials.

In this talk, I will highlight our group’s efforts in overcoming these synthesis challenges while demonstrating metallicity in epitaxial RuO2 films down to the unit cell scale. Through a combination of advanced X-ray scattering, X-ray absorption spectroscopy, transmission electron microscopy, temperature-dependent transport, magneto-optical measurements, and density functional theory (DFT) calculations, we uncover robust magnetism in epitaxially strained RuO2, consistent with an altermagnetic metallic phase [1-4]. Additionally, we reveal a novel polar phase in strained films with significant implications for electrical transport – an unexpected treat in the realm of functional oxides. I will discuss these findings in detail, emphasizing their sensitivity to material defects and structure – key ingredients that are often overlooked but crucial in determining emergent quantum phenomena.  

 bjalan@umn.edu

1.      S. G. Jeong†, I. H. Choi†, S. Nair, L Buiarelli, B. Pourbahari, J. Y. Oh, N. Bassim, A. Seo, W.

S. Choi, R. M. Fernandes, T. Birol, L. Zhao, J. S. Lee, and B. Jalan, Altermagnetic polar metallic phase in ultra-thin epitaxially-strained RuO2 films, (under review) (2025) [arxiv] †Equal contribution

2.  S. G. Jeong, I. H. Choi, S. Lee, J. Y. Oh, S. Nair, J. H. Lee, C. Kim, A. Seo, W. S. Choi, T. Low, J. S. Lee, and B. Jalan, Anisotropic Strain Relaxation-Induced Directional Ultrafast Carrier Dynamics in RuO2 Films, Sci. Adv. 11, eadw7125 (2025)

3.  S. G. Jeong, S. Lee, B. Lin, Z. Yang, I. H. Choi, J. Y Oh, S. Song, S. W. Lee, S. Nair, R. Choudhary, J. Parikh, S. Park, W. S. Choi, J. S. Lee, J. M. LeBeau, T. Low, and B. Jalan, Metallicity and Anomalous Hall Effect in Epitaxially-Strained, Atomically-thin RuO2 Films, PNAS 122(24) e2500831122

4.      S. G. Jeong, B. Y. X. Lin, M. Jin, I. H. Choi, S. Lee, Z. Yang, S. Nair, R. Choudhary, J. Parikh,

A. Santhosh, M. Neurock, K. A. Stoerzinger, J. S. Lee, T. Low, Q. Tu, J. M. LeBeau, and B. Jalan, Strain-Stabilized Interfacial Polarization Tunes Work Function Over 1 eV in RuO2/TiO2 Heterostructures, under review (2025) [arxiv]

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TH.2 AHE, Polar Systems & Correlations I    Chair:  Igor Žutić (University at Buffalo)   10:15- 12:15

TH.2.1 Symmetry lowering in epitaxial α-MnTe grown on GaAs(111) and the tuning of its anomalous Hall effect

Badih A. Assaf

Department of Physics and Astronomy, University of Notre Dame, Notre Dame IN, 46556, United States

The discovery of an anomalous Hall effect (AHE) sensitive to the magnetic state of altermagnets in hexagonal MnTe has triggered a new era of spintronics. The ability to control this AHE remains challenging. Through a combination of magnetotransport, spectroscopy and neutron scattering measurements, we provide evidence that the AHE of α-MnTe grown on GaAs(111) can be controlled by cooling down in a weak magnetic field when the magnetic point group symmetry of the system is lowered. The AHE itself exhibits a two-fold symmetry with respect to the in-plane magnetic field applied during cooldown and is vanishingly small before field cooling. Finally, neutron diffraction findings remain consistent with an easy axis orientation both with and without field cooling, suggesting that the lower symmetry favors coupling between the magnetic field and magnetic domains. Overall, our findings demonstrate how epitaxy can break magnetic domain balance, enabling a dynamic tuning of the anomalous Hall response of altermagnets.

TH.2.2 New routes to topological phases from altermagnetism: topological superconductivity and the quantized anomalous Hall effect 

Jennifer Cano

Stony Brook University, United States

Altermagnetism provides new routes to realize topological phases with vanishing net magnetization. We first propose altermagnetic heterostructures that realize topological superconductivity in one- and two-dimensions. Such platforms may offer significant improvement over a more conventional approach with uniform magnetization since the latter suppresses the superconducting gap. In the 1D case, we demonstrate that the orientation of a semiconducting wire atop an altermagnet determines its topological phase, suggesting a new experimental set-up whereby a single curved wire can host both topologically trivial and nontrivial regimes without in situ tuning. In the second part of the talk, we propose a new pathway to the quantized anomalous Hall effect (QAHE) by coupling an altermagnet to a topological crystalline insulator (TCI). The former gaps the topological surface states of the TCI, thereby realizing the QAHE in a robust and switchable platform with near- vanishing magnetization. We demonstrate the feasibility of this approach by studying a slab of the TCI SnTe coupled to an altermagnetic RuO2 layer. Our first-principles calculations reveal an induced 7 meV gap to the topological surface states, producing a finite anomalous Hall effect. Our results highlight a promising new topological platform with great tunability and applications to spintronics.

[1] Ghorashi, Hughes, Cano Phys. Rev. Lett. 133, 106601 (2024).

[2] Hadjipaschalis, Ghorashi, Cano ArXiv: 2507.00119.

[3] Jiang, Ghorashi, Lu, Cano ArXiv: 2510.15356.

TH.2.3   Magnetic polar metals by design

Pu Yu

Dept. of Physics, Tsinghua University, Beijing 100084, China

The combination of structural polarity and magnetism defines the celebrated field of multiferroics. Historically, to preserve polar order research has strategically focused on insulating systems. Consequently, magnetic polar metals remain exceptionally rare, yet they offer a unique platform where spin order, lattice distortion and conductivity can interact in profound and unexpected ways. In this talk, I will present our strategy for designing these exotic states of matter. I will begin with our discovery of Ca3Co3O8, a correlated ferromagnetic polar metal. Its structure comprises an alternating stack of tetrahedral CoO4 monolayers and octahedral CoO6 bilayers. The ferromagnetic metallic state is confined to the quasi-two-dimensional CoO6 layers, while the broken inversion symmetry arises specifically from the Co displacements. This interplay leads to pronounced nonreciprocal charge transport and a large topological Hall effect. Building on this, I will further introduce our discovery of a antiferromagnetic polar metal in the double-layered perovskite Sr3Co2O7. In this material, a distinctive structural motif with the cobalt sublattice simultaneously breaks inversion symmetry and stabilizes an A-type antiferromagnetic ground state without quenching metallicity. The most striking consequence is the observation of a pronounced zero-field anomalous Hall effect in the absence of net magnetization. This phenomenon is attributed to the collective breaking of parity-time-reversal symmetry by the intertwined antiferromagnetic and polar orders, a mechanism distinct from conventional ferromagnets. We envision these findings could open exciting avenues for exploring emergent electronic states that leverage the unique synergy between magnetism, polarity, and metallicity.

TH.2.4   Ferro-spinetic Altermagnets from Electronic Correlations

Jeroen van den Brink
Institute for Theoretical Solid State Physics, IFW Dresden, 01069 Dresden, Germany
Altermagnets are fully compensated collinear antiferromagnets that lack the combined time-reversal and translation symmetry. Here we show that their symmetry allows for a switchable ferro-spinetic polarization - the spin analogue of ferroelectricity - in a direction dictated by the lattice symmetry. We demonstrate this effect first in its purest form in an interacting altermagnetic fermion model, in which a many-body chiral symmetry forbids any charge polarization. Our quantum Monte Carlo simulations reveal edge-localized, reversible spin accumulations fully consistent with this symmetry locking. Breaking the chiral symmetry releases the charge sector: a ferroelectric polarization emerges orthogonal to the ferro-spinetic one, yielding mutually perpendicular switchable spin- and charge-polarized responses. We identify Mn-based metal-organic frameworks as realistic hosts for this effect, offering a practical route for experimental verification.
Sato, Hu, Fulga, Janson, Facio, Stroppa, Assaad & JvdB, arXiv:2510.18973 (2025)

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TH.3       Polar Systems & Correlations II    Chair:  Jorn Venderos (Drexel U. ) 13:00 – 15:30

TH.3.1 Altermagnets: Multiferroicity, Excitons, Proximity, Topology

Igor Žutić,

University at Buffalo, United States

Anisotropic and tunable spin splitting in altermagnets provides important opportunities to explore their fundamental properties and consider applications where, in more conventional systems, it is possible to integrate spintronics, electronics, and photonics [1]. For example, anisotropic spin dynamics in altermagnets [2] could improve quantum sensing [3], while multiferroic altermagnets [4-6] offer electrical control of magnetism and switching on and off spin currents that does not require magnetization reversal [4]. By using spin space group and Bethe-Salpeter equation we classify excitons in altermagnets [7]. The strain-tunability of altermagnets is also reflected in the tunability of excitons [7]. With the growing interest to design materials and emergent phenomena through proximity effects [8] we explore the implications of the altermagnetic proximity effects in the normal and the superconducting state, including tunable topological properties [9].

Work done with Tong Zhou, Yuntian Liu, Konstantin Denisov, and Jiayu David Cao.

Supported by U.S. DOE, BES Award DE-SC0004890 and AFOSR, Award FA9550-22-1-0349.

[1] P. A. Dainone et al., Nature 627, 783 (2024)

[2] K. S. Denisov, I. Žutić, Phys. Rev. B 110, L180403 (2024)

[3] V. A. S. V. Bittencourt et al., arXiv:2508.04788

[4] X. Duan et al., Phys. Rev. Lett. 134, 106801 (2025)

[5] Z. Zhu et al., Nano Lett. 25, 9456 (2025)

[6] Z. Zhu et al., Sci. China-Phys. Mech. Astron. 68,127562 (2025)

[7] J. D. Cao, K. S. Denisov, Y. Liu, I. Žutić, Phys. Rev. Lett. (in press), arXiv:2509.06790

[8] I. Žutić et al., Mater. Today 22, 85 (2019)

[9] Z. Zhu et al., arXiv:2509.06790

TH.3.2 Correlated Electronic Phenomena in Altermagnets

Rafael M. Fernandes

Department of Physics, University of Illinois Urbana-Champaign, IL 61801, USA

Altermagnets are collinear magnetically ordered systems that are invariant under a combination of time-reversal and rotational symmetries. Intense work on this topic has revealed that altermagnetism is realized in a broad range of materials, from weakly-correlated metals to strongly-correlated Mott insulators, thus opening new avenues to explore the interplay between electronic correlations and magnetism. In this talk, I will discuss two different scenarios in which either interactions promote new types of altermagnetic order or altermagnetism gives rise to unusual electronic interactions. In the first part, by focusing on kagome lattices doped close to the van Hove singularity, I will show that interactions can drive an orbital altermagnetic phase anchored on the interplay between charge order and loop-current order, which results in a collinear but non-uniform orbital magnetic phase that has the same symmetries as collinear uniform spin-altermagnetic states. Possible realizations n the recently discovered kagome metals AV3Sb5 will also be discussed. In the second part, I will show that altermagnetic fluctuations close to a putative quantum critical point promote pairing interactions that favor not only the expected triplet superconducting states, but also singlet states. The latter correspond to unconventional intra-unit-cell pairing in which the Cooper pairs are formed by electrons from different sublattices.

TH.3.3   Altermagnetism at the Frontier: Advancing Multiferroics and Topological Quantum Computing

Tong Zhou

Eastern Institute of Technology, Ningbo, China

Altermagnetism has recently emerged as a versatile platform for discovering new physical phenomena and enabling next-generation spintronic and quantum technologies. In this talk, I will discuss how altermagnetic order, when combined with ferroic degrees of freedom or topological states, opens new routes for spintronics, valleytronics, and quantum computing. I will first show how integrating ferroelectricity (ferroelasticity) with altermagnets leads to a broad family of multiferroic altermagnets—including antiferroelectric [1], ferroelectric [2], noncollinear ferroelectric [3], and ferroelastic altermagnets [4], enabling flexible electric (mechanic) control of spin and spin field-effect transistor [5]. I will then highlight how altermagnetism can provide dual protection for topological states and flexible geometric control of spin and valley transport, opening new possibilities for topological devices [6]. Finally, I will show that in hybrid structures with superconductors, altermagnets can imprint their characteristic spin textures via the proximity effect [7], driving the emergence of topological superconductivity and offering promising pathways toward robust topological quantum computing.

[1]  X. Duan, J. Zhang, Z. Zhang, I. Zutic, and T. Zhou*, PRL 134, 106801 (2025).

[2]  Z. Zhu, X. Duan, I. Zutic, and T. Zhou*, Nano Letters 25, 9456 (2025).

[3]  Z. Zhu, Y. Liu, I. Zutic, and T. Zhou*, Sci. China-Phys. Mech. Astron. 68, 127562 (2025).

[4]  R. Peng, S Fang, P Ho, T. Zhou*, J. Liu*, Y. S. Ang*, arXiv:2505.20843, npj Quant. Mater. in press.

[5]  Z. Zhu, X. Chen, I. Zutic, and T. Zhou*, arXiv:2512.02974.

[6]  X. Chen, J. Zhang, B. Hao, I. Zutic, and T. Zhou*, unpublished.

[7]  Z. Zhu, R. Huang, I. Zutic, and T. Zhou*, arXiv:2509.06790.

Email: tzhou@eitech.edu.cn

TH.3.4   Novel properties due to crystal symmetry in altermagnets

Junwei Liu

Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China

liuj@ust.hk

I will talk about novel properties due to crystal symmetry in spin-splitting antiferromagnets (AFMs) that we predicted in 2021 [1], widely known as altermagnets now, and the recent progresses [2-7]. In spin-splitting AFMs, we propose the crystal-symmetry-paired spin-valley/momentum locking (CSVL/CSML), which is enabled by crystal symmetries that intrinsically exist in AFMs. CSML enables feasible controls of spin in AFMs by manipulating the corresponding crystal symmetry. Typically, one can use a strain field to induce net valley polarization/magnetization and use an electric field to generate a noncollinear spin current even without spin-orbit coupling. We have predicted the existence of these novel properties in many real materials such as V2Se2O, V2Te2O, MnTe, and RuO2 [1] and systematically extended CSML into more general cases with noncollinear AFM orders and spin-orbit coupling considered in a very recent work [2]. All the predictions have been confirmed in experiments. Moreover, Rb or K intercalated V2Se2O and V2Te2O have been confirmed to room-temperature layered quasi-2D altermagnets [3,4], which provides suitable material platforms to explore the novel phases in 2D altermagnets.  These properties have also helped us realize the electric readout and 180o deterministic switching of the Néel order in our experimental work in Mn5Si3 [5] and CrSb [6]. More detailed discussions can be found in our recent perspective in Nature Reviews Materials [7].

[1] Haiyang Ma, et al. Nat. Commun. 12, 2846 (2021).

[2] Mengli Hu, et al. arXiv:2407.02319 (2024)

[3] Fayuan Zhang, et al. arXiv:2407.19555 (2024) [accepted by Nature Physics].

[4] Bei Jiang, et al. Nature Physics (2025) [https://doi.org/10.1038/s41567-025-02822-y].

[5] Lei Han, et al. Sci. Adv. 10, eadn0479 (2024).

[6] Zhiyuan Zhou, et al. Nature 638, 645–650 (2025).

[7] Cheng Song, et al. Nat. Rev. Mater. (2025) [https://doi.org/10.1038/s41578-025-00779-1].

TH.3.5 Atomically sharp magnetic solitons for racetrack memory at the spatial limit

K. Allen1,2, K. Du2, J. Bouaziz3, S. Mishra1,2, G. Bihlmayer3, Y. Zhang1,2, Y. Hao4, V. Ukleev5, C. Luo5, F. Radu5, Y. Gao1,2, Ch. Lane8, J.-X. Zhu8, M. Yi1,2, H. Cao4, S.-W. Cheong3,   S. Blügel3, and E. Morosan1,2

1Dept. of Physics and Astronomy, Rice University, Houston, 77005, TX, USA

2Rice Center for Quantum Materials (RCQM), Rice University, Houston, 77005, TX, USA

3Dept. of Physics and Astronomy, Rutgers University, Piscataway, 08854, NJ, USA

4PGI, FZJ, 52425 Jülich, Germany

5Neutron Scattering Division, Oak Ridge NatlLab, Oak Ridge, 37831, TN, USA

6HZB, 14109 Berlin, Germany

7Advanced Light Source, Lawrence Berkeley Natl Lab, Berkeley,100190, CA, USA

8Canadian Light Source, Inc., Saskatoon, S7N2V3, SK, Canada

9Theoretical Division, Los Alamos Nat. Lab., Los Alamos, 87545, NM, USA

Square-net lattice materials are known for hosting diverse and intriguing physical properties, from real and reciprocal-space topology to unique electronic behaviors protected by symmetry. These properties are achieved even without geometric frustration or anisotropic interactions, making them attractive candidates for studying unconventional magnetic states. In this talk, I will discuss the physics of a metallic, square-net lattice rare earth compound. This is an antiferromagnet below TN = 11.4 K, with RKKY interactions leading to magnetic frustration. The effective exchange interactions compete with the uniaxial anisotropy resulting in a rare ferrimagnetic “up-up-down” phase. As a result, the magnetization in the AFM state displays a 1/3 step (M), associated with the “up-up-down” moment configuration. More importantly, we find two additional much smaller steps (“-/+m”) at the 1/3M plateau, where m is a small induced moment (m<<M). These can be understood in a scenario where, applying a magnetic field, atomically-sharp solitons are precipitated, having all the foundational credentials for a racetrack memory at the spatial limit. The experimental evidence from field-dependent magnetization and magnetoresistance measurements is corroborated by DFT calculations relating the RKKY interaction and the magnetic anisotropy to the electronic structure. We performed atomistic spin-dynamics calculations relating the interaction parameters to the 1D magnetic soliton formation.

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TH.4    ROUND TABLE DISCUSSION 15:45 – 16:45

Moderator(s): Igor Zaliznyak  (Brookhaven National Lab )

TH.5     POSTERS 16:45 – 18:00 Chair:  Trevor Tyson (NJIT)

18:00 Adjourn. Suggested place for Dinner: Spanish Tavern, Casa Vasca or TBD in Downtown Newark

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Friday, January 16th, 2026

FR.1 Superconductivity & Piezomagnetizm     Chair:  Daniel Agterberg (University of Wisconsin)  8:00  - 10:00

FR.1.1   Topology and persistent spin currents in superconducting altermagnets

Marcel Franz

University of British Columbia, Canada

At low temperature, altermagnetic metals can naturally support spin-triplet superconducting phases with, effectively,  independent condensates for spin-up and spin-down electrons. I will show that such a state exhibits non-trivial topology with chiral or helical edge modes. In addition it can be used to both generate and carry spin-polarized persistent currents that are of interest to spintronic applications.  Theses conclusions apply to altermagnets that become intrinsically superconducting at low temperatures, but, remarkably, also to the case when an altermagnet is proximitized with a conventional spin-singlet s-wave superconductor.

FR.1.2   Anomalous Hall effect and piezomagnetism in altermagnets

Maxim Khodas

The Racah Inst. of Physics, Israel

I begin with a general exposition of altermagnetism, introducing the two-dimensional Lieb lattice as the simplest realization of this novel magnetic phase. Based on spin symmetry, I present both the altermagnetic spin splitting and non-relativistic piezomagnetism on equal footing. Following the constraints imposed by the spin-texture symmetry, I show how the Berry-curvature singularity at spin-symmetry–protected nodal lines leads to a linear, non-analytic scaling of the intrinsic Hall conductivity with the spin–orbit splitting. Next, I consider the extrinsic anomalous Hall effect in the limit of large exchange splitting. In materials with a finite Dzyaloshinskii–Moriya–type interaction, the extrinsic contribution remains essential even in the clean limit. This naturally separates altermagnetic symmetry classes into two distinct categories, differing from other classifications in the literature. Finally, I show how the spin-symmetry classification of Cooper pairs clarifies the mechanism by which piezomagnetically active strain drives the triplet superconductivity supported by altermagnetic structures into a non-unitary state.

FR.1.3   Multipolar order and piezo-response in altermagnets

Turan Birol

University of Minnesota, United States

Altermagnets host magnetic multipoles, which can be seen in their reciprocal space spin-splittings, real-space spin densities, or nontrivial Berry curvature patterns. The effect of these multipoles is also evident in the form of many response tensors, such as spin Hall or piezomagnetism which have been studied in detail. In this talk, I am going to discuss our recent first principles and tight binding results on various altermagnets, focusing on their macroscopic response to strain and magnetic fields using a symmetry-guided approach. In particular, I will show the change in magnetic multipoles under the effect of external fields, and explain their dependence (or lack thereof) on spin-orbit coupling. Finally, I will conclude by a discussion of the hidden signatures of magnetic multipoles that go beyond the commonly considered observables. 

FR.1.4   Topology and piezomagnetic effect in altermagnets from minimal models 

Jorn Venderbos

Drexel University, United States

The discovery of altermagnets has revealed intriguing properties of magnetic materials which expose connections with other phenomena. Perhaps the most interesting and consequential connection is that between altermagnetism and topology. This talk will discuss the connection between altermagnetism and topology from the perspective of minimal miscroscopic models in two dimensions. Special attention will be given to the way in which electronic topology is reflected in orbital piezomagnetism. 

________________________________________

FR.2 OPTICAL METHODS   Chair: Andrei Sirenko (NJIT)  10:15  - 12:45

FR.2.1   Chiral Hybrid Altermagnets: Symmetry‑Controlled Spin Splitting and Magneto‑Optic Kerr Effect

Li Liang1, Ding Ning1, Mingqiang Gu2, Shanshan Wang1, and Alessandro Stroppa3

1School of Physics, Southeast University, Nanjing 211189, China

2School of Flexible Electronics, Sun Yat-sen University, Shenzhen 518107, China

3CNR-SPIN, c/o Department of Physical and Chemical Sciences, University of L’Aquila, Via Vetoio I-67100 Coppito, L’Aquila, Italy.

Email: alessandro.stroppa@spin.cnr.it

Chiral organic–inorganic hybrid perovskites have emerged as versatile multifunctional materials with promising technological applications. Here, we investigate MPA₂[MnCl₄(H₂O)], a unique compound in which chirality, polarity, and altermagnetism coexist, to elucidate how these three order parameters interact and jointly govern spin splitting and Magneto-Optic Kerr (MOKE) responses. Our theoretical analysis demonstrates that the coupled states are mutually convertible through specific symmetry operations. Notably, the sign of the spin splitting reverses across the entire Brillouin zone only when chirality and polarity are inverted simultaneously, or when the magnetic order alone is reversed. In addition, reversing either chirality or magnetic order individually flips the Kerr angle, whereas polarity reversal by itself leaves the Kerr angle unchanged. These results unveil a powerful symmetry-based route to control spin transport and magneto-optical conversion through the concerted manipulation of chirality, polarity, and magnetic order—offering new opportunities for the design of low-power spintronic and optoelectronic devices.

Keywords: chiral hybrid perovskite, altermagnets, magneto-optical Kerr effect, ferroelectric, spintronics.

FR.2.2   Precision Magneto-optical Imaging of Spin-compensated Altermagnets and Antiferromagnets

Jing Xia

University of California, Irvine, United States

Spin-compensated altermagnets (AM) and antiferromagnets (AFM) offer pathways to spintronic and opto-spintronic devices with minimal stray fields, strong field tolerance, and ultrafast switching. However, detecting and spatially imaging their magnetic order has been challenging, often requiring large-scale facilities. In this talk, I will present our recent results imaging these novel magnetic states, noncollinear AFM Mn3NiN, noncoplanar AFM Co1/3TaS2, and collinear AM MnTe, using a table-top magneto-optic Kerr effect (MOKE) microscope based on a fiber-optic Sagnac interferometer. The observed MOKE signals arise from multiple mechanisms, including momentum-space Berry curvature in systems with strong spin–orbit coupling and real-space Berry curvature in systems without it. This imaging capability enables us to correlate chemical doping with magnetic symmetry and to uncover Berry-curvature density waves.

FR.2.3    Photoluminescence as a table-top probe of Altermagnetism in the Lieb-Lattice La2O3Mn2Se2

K.S. Burch

Physics Department, Boston College, United States

Altermagnetism opens a new route to correlated states that couple lattice and spin symmetries, but direct tabletop probes of the Altermagnetic (AM) state remain elusive. Here, I will discuss our efforts to fill this gap by exploring the optical response of La2O3Mn2Se2. This compound was recently reported to host a Mott-insulating AM state on the Lieb lattice, though direct evidence of such a state is elusive. First, I will discuss the optical absorption and photoluminescence (PL) measurements, which, combined with the first-principles calculations, demonstrate that La2O3Mn2Se2 is a charge-transfer insulator with a strong on-site Hubbard interaction. Furthermore, temperature, excitation-energy, and power-dependent PL measurements, together with neutron scattering, prove that it is magnon-mediated emission from a spin-forbidden (dark) state, both direct consequences of the Altermagnetism.

FR.2.4 PT-broken magnetism in orthogonally stacked CrSBr bilayers revealed by magneto-nonlinear optics

Liuyan Zhao

University of Michigan, United States

The pivotal role of broken PT symmetry in generating novel electromagnetic responses within magnetic systems has gained significant attention in recent years. While considerable efforts have focused on identifying naturally occurring magnets with broken PT symmetry, there has been comparatively little exploration into artificially engineered PT-broken magnetic structures. In this study, we fabricate a bilayer structure by aligning two CrSBr monolayers at a 90° orientation, resulting in an orthogonally stacked configuration. Structurally, this system belongs to the S4 point group, which breaks spatial inversion (P) symmetry. Magnetically, it is expected to break both spatial inversion (P) and time-reversal (T) symmetries, as well as their combined PT symmetry. We employ rotation anisotropy (RA) second harmonic generation (SHG) to probe the temperature and magnetic field dependence of the magnetic phase in the orthogonally stacked CrSBr bilayer, directly revealing its PT-broken nature.

FR.2.5 Optical studies on the monolayer altermagnet candidate

Liang Wu

UPenn, United States

The monolayer of MnP(Se,S)3 has been predicted to host the altermagnetic phase. We will present linear and nonlinear optical responses on these systems. We observe the deterministic 180 degree domain switching and will discuss the possible origins including the possibility of the monolayer altermagnet scenario. 

1.  Z. Ni, H. Zhang, D. Hopper, A. Haglund, N. Huang, D. Jariwala, L. Bassett, D. Mandrus, E.J. Mele, C.L. Kane, and Liang Wu* "Direct imaging of antiferromagnetic domains and anomalous layer- dependent mirror symmetry breaking in atomically thin MnPS3." Phys. Rev. Lett. 127, 187201 (2021) 

2.  Z. Ni, A. Haglund, H. Wang, B. Xu, C. Bernhard, X. Qian, D. Mandrus, E.J. Mele, C.L. Kane and Liang Wu* "Imaging the Neel vector switching in the monolayer antiferromagnet MnPSe3  with strain-controlled Ising order."  Nature Nanotechnology 16, 782-787 (2021)  

3.  Q. Tian, Z. Ni, et al, Unpublished.

CLOSING REMARKS & LUNCH   12:45 -14:00

Departure before 2  pm

========================

POSTERS  Jan 15th, 16:30 - 18:00

P.1 Anisotropic spin dynamics in altermagnets

K.S. Denisov, Y. Liu, and I. Zutic

University at Buffalo, State University of New York, United States

In antiferromagnets (AFM), where an exchange interaction between itinerant carriers and magnetic sublattices is site-dependent, a spin group analysis indicates the existence of AFM-material classes featuring a fully nonrelativistic spin splitting (NSS) [1-3], also referred to as the altermagnetism [3]. In this work, we demonstrate that a d-wave altermagnet has a remarkable anisotropic spin dynamic of mobile carriers, controlled by an applied magnetic field and sensitive to the interplay between the magnitude of NSS and disorder-induced relaxation from the motional narrowing effect. In contrast to the no relaxation of the spin polarization along the Neel vector, the dynamics of perpendicular spin components varies from a long relaxation for a weak NSS to the fast-decaying oscillations for a strong NSS. The latter regime is especially important for altermagnets, as the magnitude of the d-wave NSS is mainly determined by a strong atomic exchange interaction and can exceed the relaxation induced energy broadening. We demonstrate that the extreme anisotropy of the spin dynamics is transformed by the external magnetic field, which triggers the relaxation of the parallel spin component and also suppresses all the relaxation rates at larger magnitudes. In the effort to verify that a given material is an altermagnet, elucidating their magnetization and spin dynamics will provide valuable clues. Our results [4] offer experimental fingerprints to probe the emerging class of AFM featuring NSS by analyzing the transformation of the mobile carriers spin dynamics anisotropy in the applied magnetic field.

[1] L-D. Yuan, Z. Wang, J.-W. Luo, E. I. Rashba, and A. Zunger, Phys. Rev. B 102, 014422 (2020).

[2] L. Smejkal, J. Sinova, and T. Jungwirth, Phys. Rev. X 12, 031042 (2022).

[3] P. Liu, J. Li, J. Han, X. Wan, and Q. Liu, Phys. Rev. X 12, 021016 (2022).

[4] K.S. Denisov and I. Zutic, Phys. Rev. B. Lett. 110, L180403 (2024).

P.2   Symmetry Design of Physical Properties in Altermagnets: Ferroelectricities and Excitons

Yuntian Liu

University at Buffalo, State University of New York, United States

Symmetry provides a powerful framework for describing physical properties and analyzing the coupling between various degrees of freedom [1,2]. As unconventional magnets [3], particularly altermagnets [4], attract growing attention, the spin space groups (SSGs) [5,6] that characterize their symmetries have shown broad applicability. Here, we present recent advances in understanding the magnetoelectric coupling [7,8] and excitonic effects [9] in altermagnets through SSG theroy. The spin splitting in altermagnets originates from the alternating low-symmetry magnetic sublattice, enabling ferroelectric/antiferroelectric switching of spin splitting through symmetry-designed sublattice-polarization coupling, which is distinct from the conventional Néel order switching mechanisms. For the exciton properties of two-dimensional altermagnets, we develop a theoretical framework based on SSG theory to elucidate the nature of excitons in these systems and classify the combination of conduction and valence bands according to their SSG representations. Our framework provides optical fingerprints for altermagnets and reveals how their tunability is transferred to excitons.

[1] T. Zhuo, I. Žutić, Nat. Mater. 22, 284 (2023);

[2] Y. Liu, J. Li, P. Liu, Q. Liu, npj Quantum Mater. 9, 69 (2024);

[3] Q. Liu, X. Dai, S. Blügel, Nat. Phys. 21, 329 (2025);

[4] L. Šmejkal, J. Sinova, T. Jungwirth, Phys. Rev. X 12, 031042 (2022);

[5] X. Chen, J. Ren et al., Phys. Rev. X 14, 031038 (2024);

[6] X. Chen, Y. Liu et al., Nature 640, 349 (2025);

[7] X. Duan, J. Zhang et al., Phys. Rev. Lett. 134, 106801 (2025);

[8] M. Gu, Y. Liu et al., Phys. Rev. Lett. 134, 106802 (2025);

[9] J. D. Cao, K. S. Denisov, Y. Liu, I. Žutić, arXiv:2506.05753 (2025).

P.3   Improper altermagnetism

Grgur Palle, Rafael M. Fernandes

Department of Physics, University of Illinois Urbana-Champaign, IL 61801, United States

Altermagnetism is a new class of magnetism that is associated with a host of interesting phenomena, including nodal spin-splitting, piezomagnetism, magneto-optical effects, and anomalous Hall effect. To date, most studies of altermagnetism have focused on cases in which altermagnetism is the primary magnetic instability of the system. Here, we show that altermagnetism can also arise as a secondary order that accompanies a finite-momentum magnetic instability. In analogy with ferroelectrics and ferroelastic instabilities, we dub such systems improper altermagnets. We explore the necessary conditions for the appearance of improper altermagnetism, list material candidates, and explore their properties.

P.4 - W

P.5   Geometric origin of chiral magnons in antiferromagnets

Niclas Heinsdorf

UBC, Canada

Circularly polarized spin waves, so-called chiral magnons, are the fundamental carriers of information in magnonic computers, where data is processed and transmitted through spin waves instead of electric currents. Unconventional antiferromagnets (or altermagnets) have emerged as a new, promising platform for ultrafast and low-dissipation magnonics. They combine many sought-after functional properties of conventional ferro and antiferromagnets, while overcoming a central limitation of the latter -- namely, the lack of chiral magnons. We analytically demonstrate that chiral magnons in antiferromagnets arise from the quantum geometry of the electronic ground-state wave functions. This follows from an analysis of quasiparticle-pole multiplicity in the Dyson equation within the random-phase approximation. We validate the here-derived relations by computing the quantum geometry and excitation spectrum of MnF2, an altermagnetic insulator in which the existence of chiral magnons has been the subject of recent debate. We show that the nontrivial quantum metric of the material’s ground state makes altermagnetic magnon band splitting inevitable. We connect our findings to experiment by computing the circular dichroism and dynamical structure factor, which probe the system’s quantum metric and spin-wave spectrum, respectively.

P.6   A Novel K-Path Plotting Approach for Visualizing Spin Splitting in Altermagnetic Band Structures

Yujia Teng, Mesfin Eshete, Andrea Urru and Karin Rabe

Department of Physics & Astronomy, Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, United States

 Altermagnets exhibit unique momentum-dependent spin splitting that is often obscured in standard band structure plots, which plot electronic energies on the highest-symmetry points and lines. To visualize these electronic features, we present a new automatic workflow that samples general k points to show a representative picture that corresponds to Brillouin zone averages. Our novel strategy uses a general path in reciprocal space that incorporates general lines and high-symmetry lines to clearly illustrate the presence of spin splitting and sign alternation across the Brillouin zone. We present a step-by-step demonstration of this method on the altermagnet GdAuGe, and describe how researchers can access and use the tool we have developed and apply it to a crystal of any symmetry.

P.7   Systematic display of the spin splitting in band structures of altermagnetic crystals

Mesfin Eshete,1 Andrea Urru,1 Daniel, Seleznev,1,2 Yujia Teng,1 Se Young Park,3 Sebastian E. Reyes-Lillo,4 and Karin M. Rabe1

1 Department of Physics & Astronomy, Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, United States

2 Department of Physics, University of Texas at Austin, Austin, Texas 78712, United States

3 Department of Physics and Origin of Matter and Evolution of Galaxies (OMEG) Institute, Soongsil University, Seoul 06978, Korea

4 Departamento de Física y Astronomía, Universidad Andres Bello, Santiago 837-0136, Chile

In this work we demonstrate a novel approach to exhibit the unique spin splitting that is typical of altermagnets. This approach is to plot band structures on Brillouin zone paths that sample general k points to show a representative picture that corresponds to Brillouin zone averages. This is in contrast to conventional band-structure plotting which plots band structures on the highest-symmetry points and lines, and thus in many cases can fail to show any altermagnetic splitting at all. Our investigation compares the new approach with the band structures of altermagnets previously reported using conventional band structure plotting with ad hoc modifications to show the altermagnetic spin splitting. We report and compare the band structure and symmetry analysis for MnTe, CrSe, CrSb, SmFeO3, ScCrO3, LaMnO3, TlCrO3, HoFeO3, and InCrO3. This result clearly demonstrates the advantage of this novel method for displaying the spin splitting of altermagnets.

mae190@physics.rutgers.edu (mesfin.atlaw@aastu.edu.et)

kmrabe@physics.rutgers.edu

P.8   Optical Studies of RuO2 Thin Films

Benjamin Mead (UPenn, United States), Luka Mitrovic, Kyle Shen, Darrell Schlom, Liang Wu

 Rutile RuO2 was proposed as a textbook room temperature d-wave altermagnet because of its predicted large non-relativistic spin splitting. However, recent results on bulk crystals and epitaxial thin films suggest that bulk RuO2 doesn’t magnetically order. Instead, it’s proposed that thin films may magnetically order under the right strain and chemical potential. Here, I’ll present our optical magnetic circular dichroism and second harmonic generation measurements on RuO2 thin films to study their magnetic and crystal structure. Our results suggest the properties of RuO2 thin films aren’t intricately linked to sample thickness, further highlighting the need to fully characterize RuO2 thin films.

P.9 Anomalous phonon nonreciprocity in the paramagnetic phase of multiferroic CoTe6O13

Shiyu Fan1, Subin Kim1, Xianghan Xu2, and Yong Q. Cai1

1National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, United States

2School of Physics and Astronomy, University of Minnesota, Twin Cities, Minneapolis, Minnesota 55455, United States

We report the observation of non-reciprocal phonons in the paramagnetic and antiferromagnetic phases of CoTe6O13, a magnetoelectric multiferroic material with a large ferro-toroidic moment1. High resolution inelastic x-ray scattering reveals a clear energy splitting of the longitudinal acoustic (LA) branch along Γ→L compared with Γ→−L that persists up to 300 K, with a magnitude of about 0.5 to 1.0 meV. The effect is strongly anisotropic, appearing only for the c-axis longitudinal mode, while the in plane transverse modes show no detectable asymmetry. Room temperature Raman circular dichroism reveals chiral phonon modes with Eg character, suggesting intrinsic local dynamic lattice chirality. These observations are consistent with the ferro-rotational structural distortion and the associated broken mirror symmetries lifting the degeneracy between phonons propagating along ±L, so that ω(q) and ω(-q) become inequivalent in the paramagnetic state without requiring long range magnetic order. These findings highlight that phonon nonreciprocity can emerge from local structural angular momentum and lattice chirality without necessarily requiring global time reversal symmetry breaking.

[1]. X. Xu et. al., Nat. Commun. 14, 8034 (2023).

P.10 Altermagnetism in the layered intercalated transition metal dichalcogenide CoNb4Se8

Resham Babu Regmi (University of Notre Dame, United States), Hari Bhandari, Bishal Thapa, Yiqing Hao, Nileema Sharma, James McKenzie, Xinglong Chen, Abhijeet Nayak, Mohamed El Gazzah, Bence G. Márkus, László Forró, Xiaolong Liu, Huibo Cao, J. F. Mitchell, Igor I. Mazin & Nirmal J. Ghimire

Altermagnets are a new class of magnetic materials that combine the beneficial spintronics properties of ferromagnets and antiferromagnets, garnering significant attention recently [1-4]. Here, we have identified altermagnetism in a layered intercalated transition metal diselenide, CoNb4Se8, which crystallizes with an ordered sublattice of intercalated Co atoms between NbSe2 layers. Single crystals are synthesized, and the structural characterizations are performed using single crystal diffraction and scanning tunneling microscopy. Magnetic measurements reveal easy-axis antiferromagnetism below 168 K. Density functional theory (DFT) calculations indicate that A-type antiferromagnetic ordering with easy-axis spin direction is the ground state, which is verified through single crystal neutron diffraction experiments. Electronic band structure calculations in this magnetic state display spin-split bands, confirming altermagnetism in this compound. The layered structure of CoNb4Se8 presents a promising platform for testing various predicted properties associated with altermagnetism.

1.      Šmejkal, L., Sinova, J. & Jungwirth, T. Emerging research landscape of altermagnetism. Phys. Rev. X 12, 040501 (2022)

2.      Mazin, I. et al. Altermagnetism—a new punch line of fundamental magnetism. Phys. Rev. X 12, 040002 (2022).

3.      Krempasky`, J. et al. Altermagnetic lifting of Kramers spin degeneracy. Nature 626, 517 (2024)

4.      Lee, S. et al. Broken kramers degeneracy in altermagnetic MnTe. Phys. Rev. Lett. 132, 036702 (2024)

P.11 Fragility of the magnetic order in the prototypical altermagnet RuO2

Andriy Smolyanyuk (1), Igor I. Mazin (2), Laura Garcia-Gassull (3), Libor Šmejkal  (4,5,6), Roser Valentí  (3)

(1) Institute of Solid State Physics, TU Wien, 1040 Vienna, Austria

(2) George Mason University, Department of Physics & Astronomy and Center for Quantum Science and Engineering, Fairfax, Virginia 22030, United States

(3) Institut f¨ur Theoretische Physik, Goethe-Universit¨at Frankfurt, 60438 Frankfurt am Main, Germany

(4) Max Planck Institute for the Physics of Complex Systems, Dresden, Germany

(5) Max Planck Institute for Chemical Physics of Solids, Dresden, Germany

(6) Institute of Physics, Czech Academy of Sciences, Praha 6, Czech Republic

Altermagnetism is a topic that has lately been gaining attention and the RuO2 compound is among one of the most studied altermagnetic candidates. However, the survey of available literature on RuO2 properties suggests that there is no consensus about the magnetism of this material. By performing density functional theory (DFT) calculations, we show that the electronic properties of stoichiometric RuO2 are described in terms of a Hubbard U, within DFT+U, smaller than the value required to have magnetism. We further argue that Ru vacancies can actually aid the formation of a magnetic state in RuO2. This in turn suggests that a characterization of the amount of Ru vacancies in experimental samples might help the resolution of the controversy between the different experimental results. The electronic structure of RuO2 hints at a possibility of realizing a magnetically ordered state upon hole doping, and such a possibility was explored experimentally in Cr-doped RuO2, where it was suggested that this system exhibits the anomalous Hall effect (AHE) due to altermagnetism. Based on our density functional calculations, we revise the results obtained for this system and propose a different interpretation of experimental results. Our calculations suggest that extra holes are bound to Cr impurity and do not dope Ru bands, which remain nonmagnetic. Thus, the observed AHE is not due to the altermagnetism but stems entirely from magnetic Cr ions.

P.12 Circular and Vortex Polarization Signatures of a High-Field Magnetic Phase in Cu₂OSeO₃

V. A. Martinez
Department of Physics, New Jersey Institute of Technology, Newark, New Jersey 07102, United States

Copper(II) oxy-selenite (Cu₂OSeO₃), unlike most skyrmionic materials which are metallic, is an insulating and structurally chiral compound with several strong infrared-active phonons that exhibit anomalous behavior across multiple magnetic transitions at low temperatures and fields. Most previous spectroscopic studies have focused on its skyrmionic nature at low fields and frequencies. Here, we present magneto-infrared transmission with circular and vortex polarization in both Voigt and Faraday configurations, rotating analyzer ellipsometry, and circularly polarized Raman spectroscopy, revealing a field-induced regime above ~2 T with distinct magnetic modes that we ascribe primarily to on-site Cu²⁺ crystal-field (d–d) electronic transitions that interact with phonons. The observed strong circular/vortex dichroism for these coupled modes points to a weak antiferromagnetic order developing on top of the ferrimagnetic background consistent with field-driven spin canting/reorientation in fields up to 7 T in the Faraday geometry.

Various parts of this work were performed in collaboration with Andrei Sirenko, G. L. Carr, Z. Liu, P. Armitage, B.A. Trump and T.M. McQueen

The authors acknowledge the support of the NSF MPS ASCEND program for funding this research under grant number 2316535

P.13 EuAuSb: An odd-parity helical variation of altermagnetism

J. Sears,1 Juntao Yao,1,2 Zhixiang Hu,2 Wei Tian,3 Niraj Aryal,1 Weiguo Yin,1 A. M. Tsvelik,1 I. A. Zaliznyak,1 Qiang Li,1,2 and J. M. Tranquada1

1Brookhaven National Laboratory, Upton, New York 11973-5000, USA

2Stony Brook University, Stony Brook, New York 11794-3800, USA

3Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

EuAuSb is a triangular-lattice Dirac semimetal in which a topological Hall effect has been observed to develop in association with a magnetically ordered phase. Our single-crystal neutron diffraction measurements have identified an incommensurate helical order in which individual ferromagnetic Eu2+ layers rotate in-plane by ∼120◦ from one layer to the next. An in-plane magnetic field distorts the incommensurate order, eventually leading to a first order transition to a state that is approximately commensurate and that is continuously polarized as the bulk magnetization approaches saturation. From an analysis of the magnetic diffraction intensities versus field, we find evidence for a dip in the ordered in-plane moment at the same field where the topological Hall effect is a maximum, and we propose that this is due to field-induced quantum spin fluctuations. Our electronic structure calculations yield exchange constants compatible with the helical order and show that the bands near the Fermi level lose their spin degeneracy via a mechanism similar to that in the collinear altermagnets. We find that, unlike the even symmetry seen in the altermagnets, the spin splitting in EuAuSb has odd-wave symmetry similar to that recently found in a number of coplanar magnetic materials.

Phys. Rev. B 112, 094455 (2025).

P.14 Impact of strong electronic correlations on altermagnets: the case of NiS2

Ina Park

Center for Computational Quantum Physics, Flatiron Institute, New York, United States

One of the distinguishing features of an altermagnet is that its spin-up and spin-down bands display a nodal momentum-dependent splitting even in the absence of spin-orbit coupling. While this property has been investigated in many weakly-correlated altermagnetic materials, the impact of strong electron-electron interactions on the spin-dependent electronic structure has remained little explored, particularly in metals. Here, we propose NiS2 as a prototypical strongly correlated metallic altermagnet. While at ambient pressure this compound is an altermagnetic Mott insulator, it undergoes a pressure-driven metal–insulator transition (MIT) while maintaining its altermagnetic ordered phase. By systematically comparing DFT, DFT+U, and DFT+DMFT calculations on the metallic altermagnetic phase near the MIT, we disentangle how strong static and dynamic correlations modify the electronic structure. Specifically, the spin splitting of the bands is modified not only through the enhancement of the local magnetic moment caused by static correlations, but also by the momentum-dependent bandwidth renormalization caused by dynamic correlations. Moreover, dynamic electronic correlations cause a pronounced lifetime asymmetry between the spin-up and spin-down quasiparticles, an effect that is amplified by the particle–hole asymmetry promoted by Hund’s correlations. Our results not only shed light on the rich landscape of correlation effects in metallic altermagnets, but also establishes NiS2 as a platform to investigate the interplay between Mott and Hund physics and altermagnetic order.

P. 15  Magneto-Optical Study of Chiral Magnetic Modes in NiI2: Direct Evidence for Kitaev Interactions

Kartik Panda, Daniel Bazyliansky, and Nimrod Bachar

Department of Physics, Ariel University, Ariel, 4070000, Israel

NiI2, recently classified as a p-wave magnet, is a van der Waals (vdW) two-dimensional magnetic material [1, 2]. In this poster, I will present our magneto-optical study revealing the magnetic excitations in the multiferroic antiferromagnet NiI2, challenging existing models and opening new pathways for understanding topological magnetism [3]. We observe two distinct collective modes at 34 cm⁻¹ and 37 cm⁻¹ at 4.2 K, deep within the helical AFM ground state, well below the Neel temperatures TN1 ≈ 76 K and TN2 ≈ 59 K [2,4]. These modes exhibit an anisotropic blueshift with increasing magnetic field, with the higher-energy mode shifting nearly twice as much (2 cm⁻¹) compared to the lower one (1 cm⁻¹) under a 16 T applied field. The circular optical conductivity shows a dichroic response, with the magnon excitations exhibiting opposite chirality. While earlier studies attributed these electromagnon modes to a simple spin helical model, our new data contradict this view [3], and instead, we propose that the spectra are better explained by a modified Kitaev exchange interaction model, highlighting the role of bond-dependent anisotropic interactions. These findings place NiI2 as a promising platform for exploring topological magnetism, where Kitaev interactions can stabilize exotic magnetic textures, such as high-order skyrmion lattices [5]. This system offers a tunable platform for investigating the interplay between chirality, anisotropy, and topology in low-dimensional magnets.

[1] Q. Song et al. Nature 642, 64–70 (2025).

[2] Q. Song et al. Nature 602, 601–605 (2022).

[3] K. Panda et al. arXiv:2511.06093 (2025).

[4] Jae Ha Kim et al. Phys. Rev. B 108, 064414 (2023).

[5] C. Kim et al.  arXiv:2502.14167 (2025)

P.16   W

Structural origin of resonant diffraction in RuO2

Connor A Occhialini1,2, Christie Nelson1, Alessandro Bombardi3, Shiyu Fan1, Raul Acevedo-Esteves1, Riccardo Comin4, Dmitri N Basov2, Maki Musashi5, Masashi Kawasaki5,6, Masaki Uchida7,8, Hoydoo You9, John Mitchell9, Valentina Bisogni1, Claudio Mazzoli1, Jonathan Pelliciari1

1Brookhaven National Laboratory, United States

 2Columbia University

 3Diamond Light Source

 4Massachusetts Institute of Technology

 5University of Tokyo

 6RIKEN

 7Institute of Science Tokyo

 8Toyota Physical and Chemical Research Institute

 9Argonne National Laboratory

We report Ru L3-edge resonant X-ray diffraction studies on single crystal and (001) oriented epitaxial films of RuO2. We investigate the distinct Q = (100) and (001) reflections as a function of incident energy, azimuthal angle, and temperature. The results show that the observed resonant diffraction in RuO2 is fully consistent with a resonant charge anisotropy signal of structural origin permitted by the parent (non-magnetic) rutile P42/mnm space group. These results significantly constrain the magnetic contribution to the resonant diffraction signal and indicate the unlikely existence of k=0 antiferromagnetic order in RuO2.

https://arxiv.org/abs/2510.13767

P.17    From Microscopic Imaging to Ultrasensitive Sagnac interferometry in van der Waals Spintronics and Beyond

Kelly Luo

University of Southern California, United States

The ability to image and manipulate magnetic order at the microscopic scale is essential for advancing spintronic applications in low-dimensional magnetic and topological systems. In this poster, we highlight recent progress in our group that combines microscopic magnetic imaging with ultrasensitive optical interferometry to study spintronic responses in van der Waals and related magnetic systems.

We discuss how nanoscale imaging techniques provide direct insight into complex magnetic textures and interfacial effects in layered heterostructures, while complementary fiber-based Sagnac magneto-optical interferometry enables quantitative detection of spin–orbit torques in materials that are challenging to access electrically. Together, these approaches illustrate a flexible experimental framework for probing spin–orbit physics across a broad class of quantum materials, including emerging altermagnetic platforms

P.18  Signatures of Z3 Vestigial Potts-nematic order and imaging of nematic inhomogeneity in a van der Waals antiferromagnet

Qi Tian,1 Zhuoliang Ni,1 Daniil S. Antonenko,2,3 W. Joe Meese,4 Matthew Cothrine,5 Nan Huang,5 Amanda V. Haglund,5 Tony Tzolov,1 David G. Mandrus,5 Rafael M. Fernandes,4 Jörn Venderbos,3,6 and Liang Wu1

1Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA

2Department of Physics, Yale University, New Haven, Connecticut 06520, USA

3Department of Physics, Drexel University, Philadelphia, Pennsylvania 19104, USA

4School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA

5Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, U.S.A.

6Department of Materials Science & Engineering, Drexel University, Philadelphia, PA 19104, USA

 Layered van der Waals magnets have attracted much recent attention as a promising and versatile platform for exploring intrinsic two-dimensional magnetism. Within this broader class, the transition metal phosphorous trichalcogenides MPX3 stand out as particularly interesting, as they provide a realization of honeycomb lattice magnetism and are known to display a variety of magnetic ordering phenomena as well as superconductivity under pressure. One example, found in a number of different materials, is commensurate single-Q zigzag antiferromagnetic order, which spontaneously breaks the spatial threefold (C3) rotation symmetry of the honeycomb lattice. The breaking of multiple distinct symmetries in the magnetic phase suggests the possibility of a sequence of distinct transitions as a function of temperature, and a resulting intermediate Z3-nematic phase which exists as a paramagnetic vestige of zigzag magnetic order– a scenario known as vestigial ordering. Here, we report the demonstration of vestigial Potts-nematic order in rhombohedral FePSe3. By performing linear dichroism imaging measurements to probe rotational symmetry breaking and rotational anisotropic SHG to track the onset of AFM order, we find that the C3 symmetry is already broken above the Néel temperature. We show that these observations are explained by a general Ginzburg-Landau model of vestigial nematic order driven by magnetic fluctuations and coupled to residual strain. An analysis of the domain structure as temperature is lowered and a comparison with zigzag-ordered monoclinic FePS3 reveals a broader applicability of the Ginzburg-Landau model in the presence of external strain, and firmly establishes the MPX3 magnets as a new experimental venue for studying the interplay between Potts-nematicity, magnetism and superconductivity.

SEVERAL TALKS FROM THE PREVIOUS Altermagnetism Workshop January 2025

Address for taxi, Uber, walk: 355 Martin Luther King Junior Blvd., Newark, NJ 07102

Address for Parking Garage: 154 Summit Str., Newark, NJ 07102

PARKING

REQUEST for FREE PARKING at NJIT (submit before Jan 12th, 2026)

https://forms.gle/sUY3qNczELxSZuDv8

Personal or rental car parking is free upon filling out the online parking request form sent by Andrei Sirenko to registered participants. Entrance to the garage is permitted only during designated times and exit permitted at any time. Overnight parking permitted. For navigation to the parking garage: 

154  Summit Street, Newark, NJ 07102    

Walking time to the  Workshop is 2 min

Just in case, an ATM is located at the street level of the Campus Center.

WiFi Internet access:

There are two wireless networks in the Workshop area:

1. NJITguest - OPEN network, no password, but a sign-on  is required meaning you will need to receive a text or email message sent for identification. The procedure is similar to that for free WiFis at the big International Airports. This network is OK for text messaging, but is sometimes too slow for video. 

https://ist.njit.edu/connecting-njitguest

2.   eduroam  -  is the same WiFi as at the most Universities in USA and EU.  An account is needed, so if you are coming from a University, its a good idea to activate your account in advance.  

Preparation of a Backup copy of the talks/posters on a memory stick is strongly advised.

List of Hotels in Downtown Newark:

Robert Treat Hotel

Courtyard by Marriott Newark Downtown

TRYP by Wyndham Newark Downtown

DoubleTree by Hilton Newark Penn Station

List of Restaurants in Downtown Newark:

Fornos of Spain    https://fornosofspain.com/ 
Free valet parking at the restaurant,  ~$80/person  without drinks

Casa Vasca         
https://www.casavasca.net/
Limited free parking at the restaurant, ~$50/person without drinks

Tony Da Caneca, ~$60/person   without drinks

 https://tonydacanecarestaurant.com/

Spanish Tavern,   ~$60/person  without drinks
https://spanishtavernnewark.com/

Fernandes 2  Steak House, Free parking at the restaurant, ~$60/person   without drinks 

Reservations by phonecalls
https://www.fernandessteakhouse.com/    

Sabor Unido   https://saborunido.com/  

~$40/person   without drinks

More info about local restaurants is here:

https://www.tripadvisor.com/Restaurants-g46671-zfn20483951-Newark_New_Jersey.html

Dinner will not be provided by the workshop so we encourage small groups to arrange their own dinner

reservations. We can assist with coordinating dinner reservations for 4 - 6 people during the Workshop days  around lunch time. Participants with cars are encouraged to take a lead in making reservations and helping with transportation to the restaurants. Reservations can be made using restaurant websites and/or https://www.opentable.com/.  Usually restaurant bills can be split upon request between several guest's credit cards at the same table. Restaurants prefer "even splits" of the final bill. Preparing small bills in advance to settle the order differences is suggested. Cash always works. Also, "house wine" or/and "sangria pitchers", which cost much less compared to wine bottles, are available in all of the aforementioned restaurants. The main course dishes are usually large, so additional appetizers are not really necessary. Complimentary bread, olives, and even salads are provided for the table in most of the aforementioned restaurants.  

Participants are strongly encouraged to drive or use Uber / Lyft / Taxi between their Hotels, Restaurants  and the Workshop locations.

Dining options around NJIT Campus are limited due to the Winter Break.

Cultural events in the area:

MET Opera in NYC. Bizet Carmen is on the stage on Jan 14th and Bellini  I Puritani   is on the stage on Jan 15th

  https://www.metopera.org/

Breakfast, Lunch, and 4pm Coffee breaks

Breakfast, lunch and coffee during breaks will be provided by the workshop. 

Additional healthy / vegetarian options may be available for purchase in the "Farmer's Fridge" across the street:   350 Dr Martin Luther King Jr Blvd, Newark, NJ 07102   (open till 4 pm).

Lunch at the conclusion of the workshop on Friday Jan 16th at 12:30 pm will be offered only upon request using the google form