Book of abstracts
Paul C. Canfield
Ames Laboratory, Iowa State University, Ames, Iowa 50010, USA
Department of Physics, Iowa State University, Ames, Iowa 50010, USA
Over the past 30 plus years my group has made over 10,000 solution growth attempts to grow or explore 1,000’s of different compounds or phase spaces. Over the past decade we have been developing a variety of different algorithms for identifying and accessing poorly explored spaces, partly with an eye toward discovering new phases, partly with an eye toward discovering new electrical or magnetic phase transitions and ground states. In this talk I will try to address the basic research questions of, “where should I look for new materials or physics?” and “how can I enhance my chances of discovering X, Y, or Z (where XYZ can be your favorite state, structure or behavior)?”. Specific examples spanning superconductors, quasicrystals, heavy fermions, fragile magnets, topological electronic systems, local moment magnets and a few lost puppies will be given and reviewed.
The goal of this talk is to inspire and entertain, any resemblance to persons living or dead is coincidental. This talk is based on parts of my recent review article, “New Materials Physics” [1] as well as recent technical papers on solution growth. [2,3]
[1] P. C. Canfield, Rev. Prog. Phys. 83, 016501 (2020).
[2] T. J. Slade and P. C. Canfield, Z. Anorg. Allg. Chem., 648, e202200145 (2022)
[3] P. C. Canfield, T. Kong, U. S. Kaluarachchi, N-H. Jo, Philosophical Magazine 96, 84-92 (2016)
Sara Haravifard
Duke University
Frustrated magnets, particularly those based on triangular lattice geometries, are prime candidates for hosting exotic quantum states driven by strong correlations and geometric frustration. In this talk, I will present recent work on newly synthesized rare-earth-based triangular lattice materials that provide clean platforms for exploring such phenomena. Through comprehensive thermodynamic and neutron scattering studies on high-quality single crystals, we uncover signatures of unconventional magnetic ground states. These include evidence for a quantum spin liquid state characterized by fractionalized excitations, as well as a distinct quantum disordered state with hidden multipolar state. These findings underscore the potential of triangular lattice systems in advancing our understanding of quantum magnetism and the emergence of novel phases of matter.
Mohammad Hafezi
University of Maryland
First, I discuss how optical probes can reveal various aspects of magnetism in 2D materials. In particular, I report the first observation of quantum anomalous Hall states in twisted bilayer WSe₂, made possible by optically measuring the average magnetization ⟨S⟩. Next, I explain how one can access higher-order observables such as ⟨S·S⟩ and ⟨S·(S×S)⟩ by measuring higher-order correlations of scattered photons. Such an approach could enable unambiguous detection of chiral spin liquids. Finally, inspired by progress in cold atom systems, I introduce a method to optically engineer magnetic Hamiltonians, such as a generalized Heisenberg model.
Ceren B. Dag
Indiana University, Bloomington
Strongly coupling materials to cavity fields can affect the material’s electronic properties altering the phases of matter. In this talk, I will first discuss the monolayer graphene whose electrons can be coupled to both left and right circularly polarized vacuum fluctuations, and time-reversal symmetry is broken due to a phase shift between the two polarizations. We develop a many-body perturbative theory, and derive cavity-mediated electronic interactions by utilizing Schrieffer-Wolff transformation. This theory leads to a gap equation which predicts a topological band gap at Dirac nodes in vacuum. Moving forward, I will demonstrate how the quantum nature of photons affects the topology of the correlated photo-electron hybrid wave function. One of our central findings is a fundamental relation between the Berry phase and the properties of exchanged photons with matter at light-matter hybridization points in the Brillouin zone. This physics turns out to be generic, as it also emerges in Bernal stacked bilayer graphene. A subtle competition between cavity frequency and interlayer tunneling emerges in graphene stacks that is responsible for topological phase transitions in light-matter Hilbert space and that cannot be captured by mean-field theory in vacuum. A systematic exploration of multilayer graphene heterostructures and stacking configurations in a chiral tHz cavity reveals that linear dispersion enhances the low-energy cavity-induced topological gap. Furthermore, introducing a displacement field drives the low-energy vacuum band from valley-Chern to Chern insulator in bilayer and chiral-stacked multilayer configurations, comprising a gate-tunable topological phase transition. Our findings pave the way for future control and engineering of graphene heterostructures with chiral cavity fields.
Roger Pynn
Indiana University, Bloomington and Oak Ridge National Laboratory
Neutron scattering has been used for over 70 years to probe static and dynamic correlations in matter and has provided fundamental information about materials as different as polymers and quantum liquids. I will briefly explain the overall capabilities of neutron scattering and then discuss in more detail the use of polarized neutrons to study problems such as magnetism in thin films, magnetic ordering in multiferroics and excitations in exotic quantum magnets. I will then describe some more recent work we have done at IU exporing mode entanglement of neutrons that can be exploited for quantum enhanced measurements. Finally, I will speculate about the possibility of using entangled neutrons to probe entanglement in matter.
Andrew D. Christianson
Oak Ridge National Laboratory
In quantum magnetism, elegantly simple model systems can exhibit rich behavior that enables the testing of fundamental ideas, which in turn form the basis for understanding and identifying more complex phenomena. In this talk, several examples of model quantum magnetism will be presented where the classical regime can be accessed through temperature or applied magnetic fields, and where the spin Hamiltonian can be accurately determined from inelastic neutron scattering data.
YbCl₃ is a nearly ideal realization of an effective S = 1/2 nearest-neighbor Heisenberg model on the honeycomb lattice. I will discuss how quantum effects renormalize both single-magnon and multi-magnon excitations, and how this renormalization can be tuned—and ultimately driven to the classical limit—by applying a magnetic field. From a broader perspective, this work demonstrates that structures within magnetic continua can emerge over a wide experimental parameter space, providing an additional means of identifying quantum phenomena.
To explore how tuning toward the classical regime via temperature can yield insights into quantum magnetism, the S = 1/2 Heisenberg antiferromagnet Zn₂VO(PO₄)₂ and the S = 1/2 XXZ triangular lattice antiferromagnet Ba₂La₂CoTe₂O₁₂ will be discussed. Notably, this approach has successfully enabled the determination of spin Hamiltonians by fitting energy-resolved excitation spectra in the paramagnetic phase, while also capturing the attenuation of quantum spin dynamics—such as continuum excitations—due to thermal fluctuations.
Kaden Hazzard
Rice University
Ultracold molecules' internal degrees of freedom open exciting avenues to explore quantum magnetism. I will discuss two examples: (1) Shielded molecules' hyperfine states realize SU(N) magnetism with tunable (including attractive) interactions, both fermions and bosons, and N up to 36 (or more). This circumvents limitations of SU(N) magnets realized in ultracold alkaline-earth atoms, which have only repulsive interactions, fermions, and N no greater than 10. I will describe how this symmetry emerges and the many-body physics arising from attractive interactions. (2) Experiments can use rotational states to create synthetic dimensions -- effective extra spatial dimensions where rotational states and microwave-driven transitions between them mimic lattice sites and tunneling, respectively. I will describe the remarkable experimental progress and intriguing physics, such as quantum strings. With just a few rotational levels, the systems become spin models that can harbor paraparticles, quasiparticles that are neither fermions nor bosons and, unlike anyons, can exist in three dimensions.
Nai-Chang Yeh
Department of Physics, California Institute of Technology, Pasadena, CA 91125
Two-dimensional (2D) van der Waals (vdW) materials, such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDs), exhibit a rich variety of physical properties that can be further tailored to achieve novel functionalities and emergent quantum phenomena by strain engineering and light-matter interaction. In the case of monolayer (ML) graphene, nontrivial strain can induce giant pseudomagnetic fields (PMF), leading to modifications of the 2D electronic correlation and bandstructures. By nanoscale strain engineering the strength and spatial distribution of PMF in ML graphene, we demonstrate the emergence of quantum oscillations as well as quantum valley Hall and quantum anomalous Hall effects from strain ML-graphene devices without any external magnetic field.[1,2] In the case of semiconducting ML-TMDs, strain is known to modify the bandstructures and result in reduced energy gaps, which can be harnessed to achieve desirable trapping potential landscapes for excitons under optical illumination and result in enhanced optical emission and strong electronic bandstructure renormalization in the strained region, as revealed by our recent studies using laser-assisted scanning tunneling microscopy/spectroscopy.[3] Moreover, structured light, which refers to photons with finite spin or orbital angular momentum (SAM or OAM) such as circularly polarized light with SAM σ = ±1 and twisted light with OAM l=±1, ±2, ±3 , can exert novel controls on ML-TMDs.[4,5] In particular, we find that the g-factor in ML-TMDs is greatly enhanced (~ 12) under SAM light due to the increased population of intervalley excitons in the presence of magnetic fields, and that photocurrents in ML-TMD devices exhibit rapid increase with increasing |l| due to the increased population of Rydberg excitons under OAM light.[6] Finally, we discuss the feasibility of developing a new platform of solid-state quantum simulators for interacting excitons[3] based on the controllability of the electronic, optoelectronic and photonic properties of ML-TMDs by strain and structured light.
References:
[1] “Nanoscale engineering of giant pseudo-magnetic fields, valley polarization and topological channels in strained graphene”, C.-C. Hsu, M. L. Teague, J.-Q. Wang, and N.-C. Yeh*, Science Advances 6, aat9488 (2020).
[2] “A perspective of recent advances in PECVD-grown graphene thin films for scientific research and technological applications”, C.-H. Lu, D. Hao, and N.-C. Yeh*, Materials Chemistry and Physics 319, 129318 (2024).
[3] “Strongly enhanced electronic bandstructure renormalization by light in nanoscale strained regions of monolayer MoS2/Au(111) heterostructures”, A. Park, R. Kantipudi, J. Göeser, Y. Chen, D. Hao, and N.-C Yeh*, ACS Nano 18 (43), 29618 – 29635 (2024).
[4] “Dramatically enhanced valley-polarized emission of monolayer WS2 at room temperature with plasmonic Archimedes spiral nanostructures and gated control”, W.-H. Lin*, P. C. Wu, H. Akbari, G. R. Rossman, N.-C. Yeh*, and H. A. Atwater*, Advanced Materials 34 (3), 2104863 (2022).
[5] “Control of trion-to-exciton conversion in monolayer WS2 by orbital angular momentum of light”, R. Kesarwani, K. B. Simbulan, T.-D. Huang, Y.-F. Chiang, N.-C. Yeh*, Y.-W. Lan*, and T.-H. Lu*, Science Advances 8, eabm0100 (2022).
[6] “Cryogenic scanning photocurrent spectroscopy for materials responses to structured optical fields”, D. Hao, C.-I Lu, Z. Sun, Y.-C. Chang, W.-H. Chang, Y.-R. Chen, A. Park, B. Rao, S. Qiu, Y.-W. Lan*, T.-H. Lu* and N.-C. Yeh, submitted (2025).
Ana Maria Rey
JILA, NIST and University of Colorado at Boulder
Recent experimental developments on cooling, trapping, and manipulating ultra-cold dipolar gases are opening a door for the controllable study of their complex many-body quantum dynamics. In particular, by encoding a spin degree of freedom in rotational levels in polar molecules it is now possible to use these systems to emulate a variety of rich spin models exhibiting long range and anisotropic interactions. In this talk, I will discuss theoretical and experimental progress [1,5] towards engineering quantum spin models relevant for quantum simulation and sensing in molecule arrays trapped in 3D optical lattices or optical twezers.
[1] Magnetically Tunable Electric Dipolar Interactions of Ultracold Polar Molecules in the Quantum Ergodic Regime, Rebekah Hermsmeier, Ana Rey, Timur Tscherbul, Physical Review Letters 133, 143403 (2024).
[2] Observation of Generalized t-J Spin Dynamics with Tunable Dipolar Interactions, Annette Carroll, Henrik Hirzler, Calder Miller, David Wellnitz, Sean Muleady, Junyu Lin, Krzysztof Zamarski, Reuben Wang, John Bohn, Ana Maria Rey, Jun Ye, arXiv:2404.18916, Science in press (2025).
[3] Tunable momentum pair creation of spin excitations in dipolar bilayers
Thomas Bilitewski, G. Domínguez-Castro, David Wellnitz, Ana Rey, Luis Santos, Physical Review A 108, 013313 (2023)
[4] Manipulating Growth and Propagation of Correlations in Dipolar Multilayers: From Pair Production to Bosonic Kitaev Models Thomas Bilitewski, Ana Maria Rey, Physical Review Letters 131, 053001 (2023).
[5]Entanglement and iSWAP gate between molecular qubits
Lewis Picard, Annie Park, Gabriel Patenotte, Samuel Gebretsadkan, David Wellnitz, Ana Rey, Kang-Kuen Ni, Nature 637, 821–826 (2025).
Haidong Zhou
University of Tennessee, Knoxville
One obstacle is that most of the studied quantum magnets are insulators and electronically inert, which is incompatible with an electrical circuit that relies on moving charge carriers. The grand challenge is to find a way to convert the entanglement information into mobile charge signal by “metallizing” quantum magnets.
In this talk, I will introduce a unique approach by designing and synthesizing new heterostructures based on geometrically frustrated magnets to address this obstacle. I will give two examples: (i) Dy2Ti2O7/Bi2Ir2O7 heterostructure in which the transport data measured on the Bi2Ir2O7 reflects the Kagome spin ice broken phase transition of the underlying Dy2Ti2O7 crystal [1]; (ii) Yb2Ti2O7/Bi2Ir2O7 heterostructure in which the abnormal magnetoresistance of the Bi2Ir2O7 film strongly correlates the strong quantum spin fluctuations in Yb2Ti2O7.
[1] H. Zhang et al, Anomalous magnetoresistance by breaking ice rule in Bi2Ir2O7/Dy2Ti2O7 heterostructure, Nature Communications 14, 1014(1-7) (2023).
[2] C. Xing et al, Anomalous proximitized transport in metal/quantum magnet heterostructure Bi2Ir2O7/Yb2Ti2O7, Physical Review Materials 8, 114407 (2024).
Axel Hoffmann
Materials Research Laboratory and
Department of Materials Science and Engineering,
The Grainger College of Engineering
University of Illinois Urbana-Champaign, Urbana, Illinois 61801, U.S.A.
Magnons readily interact with a wide variety of different excitations, including microwave and optical photons, phonons, and other magnons. Such hybrid magnon dynamic excitations have recently gained increased interest due to their potential impact on coherent information processing [1]. This in turn opens new pathways for hybrid quantum information systems [2–4]. I will discuss specific examples and strategies, where we developed fully integrated devices that form the essential building blocks for more complex integrated coherent quantum systems. Towards this end, we demonstrated strong magnon-photon coupling in scalable coplanar devices using coplanar superconducting microwave photon resonators [5]. Based on this concept we have shown how two magnon resonators can be coupled over macroscopic distances, and using local time-resolved detection, we demonstrate coherent, Rabi-like, energy exchange between them [6]. Conversely, photons in two separate coplanar waveguides can be transmitted in a directional manner via nonreciprocal coupling to magnons [7]. Lastly, I will show how a superconducting qubit can be used for sensitively detecting magnon populations over a broad dynamic range [8]. These measurements illustrate the potential of using magnons for coherently controlled interactions ultimately even in the single quantum limit.
This work was supported by the U.S. Department of Energy, Office of Science, Materials Sciences and Engineering Division under Contract No. DE-SC0022060.
References
Y. Li, et al., J. Appl. Phys. 128, 130902 (2020).
D. D. Awschalom, et al., IEEE Quantum Engin. 2, 5500836 (2021).
Y. Li, et al., 2022 IEEE Intern. Electr. Dev. Meeting, 14.6.1 (2022).
Z. Jiang, et al., “Appl. Phys. Lett. 123, 130501 (2023).
Y. Li, et al., Phys. Rev. Lett. 123, 107701 (2019).
M. Song, et al., arXiv:2309.04289.
Y. Li, et al., Phys. Rev. Lett. 124, 117202 (2020).
S. Rane, et al., arXiv:2412.11859.
Chong Zu
Washington University, St. Louis
In this talk, I will introduce our recent efforts on the use of nitrogen-vacancy (NV) centers in diamond and boron-vacancy (VB) centers in hexagonal boron nitride as a non-invasive and table-top quantum sensor to probe different aspects of static and dynamic magnetic signals in quantum materials. In particular, we will focus on (1) the diagnosis of critical fluctuations and vortex dynamics in thin-film high-Tc cuprate superconductor, BSCCO [1]; and (2) the imaging of pressure-driven magnetic phase transition in room-temperature self-intercalated van der Waals ferromagnet, Cr{1+δ}Te2 [2];
[1] arXiv:2502.04439
[2] arXiv:2501.03319