Embedded Files
Some Recent Publications
Some Recent Publications
Elastic Response and Instabilities of Anomalous Hall Crystals
Félix Desrochers, Mark R. Hirsbrunner, Joe Huxford, Adarsh S. Patri, T. Senthil, Yong Baek Kim
Anomalous Hall crystals (AHCs) are exotic phases of matter that simultaneously break continuous translation symmetry and exhibit the quantum anomalous Hall effect. AHCs have recently been proposed as an explanation for the observation of an integer quantum anomalous Hall phase in a multilayer graphene system. Despite intense theoretical and experimental interest, little is known about the mechanical properties of AHCs. We study the elastic properties of AHCs, first by utilizing a continuum model with uniform Berry curvature. In contrast to Wigner crystals, we find that the stiffness of the AHC weakens and eventually vanishes as electronic interactions are increased. Furthermore, we demonstrate that the triangular lattice AHC arising in an experimentally relevant parameter regime of a realistic model of rhombohedral pentalayer graphene is unstable, emphasizing the importance of understanding the mechanical properties of AHCs for interpreting experiments.
arXiv:2503.08784 (2025)
Emergent photons and fractionalized excitations in a quantum spin liquid
Bin Gao, Félix Desrochers, Diana Kirschbaum, David W. Tam, Paul Steffens, Arno Hiess, Yixi Su, Sang-Wook Cheong, Silke Paschen, Yong Baek Kim, Pengcheng Dai
A quantum spin liquid (QSL) arises from a highly entangled superposition of many degenerate classical ground states in a frustrated magnet, and is characterized by emergent gauge fields and deconfined fractionalized excitations (spinons). The 3D pyrochlore lattice of corner-sharing tetrahedra can host a QSL with U(1) gauge fields called quantum spin ice (QSI), which is a quantum (with effective S=1/2) analog of the classical (with large effective moment) spin ice. A key difference between QSI and classical spin ice is the predicted presence of the linearly dispersing collective excitations near zero energy, dubbed the "photons", arising from emergent quantum electrodynamics, in addition to the spinons at higher energies. Recently, 3D pyrochlore systems Ce2M2O7 (M = Sn, Zr, Hf) have been suggested as effective S=1/2 QSI candidates. Here, we use polarized neutron scattering experiments on single crystals of Ce2Zr2O7 to conclusively demonstrate the presence of magnetic excitations near zero energy at 50 mK as a promising evidence for emergent photons, in addition to signatures of spinons at higher energies.
To appear in Nature Physics (2025)
Observation of a non-Hermitian supersonic mode on a trapped-ion quantum computer
Yuxuan Zhang, Juan Carrasquilla, Yong Baek Kim
Quantum computers have long been anticipated to excel in simulating quantum many-body physics. While most previous work has focused on Hermitian physics, we demonstrate the power of variational quantum circuits for resource-efficient simulations of dynamical and equilibrium physics in non-Hermitian systems, revealing new phenomena beyond standard Hermitian quantum machines. Using a variational quantum compilation scheme for fermionic systems, we reduce gate count, save qubits, and eliminate the need for postselection, a major challenge in simulating non-Hermitian dynamics via standard Trotterization. Experimentally, we observed a supersonic mode in the connected density-density correlation function on a fermionic chain after a non-Hermitian, locally interacting quench, which would otherwise be forbidden by the Lieb-Robinson bound in a Hermitian system. Through a trapped-ion implementation on the Quantinuum H1 quantum processor, we accurately capture correlation functions and energies across an exceptional point on a dissipative spin chain.
To appear in Nature Physics (2025)
Spectroscopic signatures of fractionalization in octupolar quantum spin ice
Félix Desrochers, Yong Baek Kim
Recent investigations on the dipolar-octupolar compounds Ce2Zr2O7 and Ce2Sn2O7 suggest that they may stabilize so-called π-flux octupolar quantum spin ice (π-O-QSI), a novel three-dimensional quantum spin liquid hosting emergent photons. In this Letter, we thoroughly investigate O-QSI using an extension of gauge mean-field theory. This framework produces a phase diagram consistent with previous studies and an energy-integrated neutron scattering signal with intensity-modulated rod motifs, as reported in experiments and numerical studies. We predict that the dynamical spin structure factor of π-O-QSI is characterized by a broad continuum with three distinctive peaks as a consequence of the two mostly flat spinon bands. These three peaks should be measurable by high-resolution inelastic neutron scattering. Such spectroscopic signatures would be clear evidence for the realization of π-flux quantum spin ice.
Phys. Rev. Lett. 132, 066502 (2024)
Evidence for Fractional matter coupled to the emergent gauge field in a quantum spin ice
Victor Porée, Han Yan, Félix Desrochers, Sylvain Petit, Elsa Lhotel, Markus Appel, Jacques Ollivier, Yong Baek Kim, Andriy H. Nevidomskyy, Romain Sibille
Quantum spin ice (QSI) is a theoretically well-established example of quantum spin liquid and described by an emergent quantum electrodynamics, with excitations behaving like photon and matter quasiparticles. Our experimental colleagues use backscattering neutron spectroscopy to achieve extremely high resolution of the time-dependent magnetic response of the candidate QSI material Ce2Sn2O7. The experiments find a gapped spectrum featuring peaks that match theories for pair production and propagation of fractional matter excitations (spinons). We show that the multiple peaks are a specific signature of the π-flux phase of QSI, providing spectroscopic evidence for fractionalization in a three-dimensional quantum spin liquid.
Nature Physics volume 21, pages83–88 (2025)
Intertwined van-Hove Singularities as a Mechanism for Loop Current Order in Kagome Metal
Heqiu Li, Yong Baek Kim, Hae-Young Kee
Recent experiments on Kagome metals AV3Sb5 (A=Cs,Rb,K) indicated spontaneous time-reversal symmetry breaking in the charge density wave state in the absence of static magnetization. The loop current order (LCO) is proposed as its cause, but a microscopic model explaining the emergence of LCO through electronic correlations has not been firmly established. We show that the coupling between van-Hove singularities (vHS) with distinct mirror symmetries is a key ingredient to generate LCO ground state.
Phys. Rev. Lett. 132, 146501 (2024)
Google Sites
Report abuse