Bulletin of the American Physical Society
2024 APS March Meeting
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session M22: Frustrated Magnetism: Kagome and Kitaev MagnetsFocus

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Sponsoring Units: GMAG Chair: Xiaojian Bai, Louisiana State University Room: 101B 
Wednesday, March 6, 2024 8:00AM  8:12AM 
M22.00001: Emergent spingapped magnetization plateaus in a spin1/2 perfect kagome antiferromagnet Shota Suetsugu, Tomoya Asaba, Yuichi Kasahara, Yuhki Kohsaka, Keisuke Totsuka, Boqiang Li, Yuqiang Zhao, Yuesheng Li, Masashi Tokunaga, Yuji Matsuda The twodimensional (2D) spin1/2 kagome Heisenberg antiferromagnet is believed to host quantum spin liquid (QSL) states with no magnetic order, but its ground state remains largely elusive. An important outstanding question concerns the presence or absence of the 1/9 magnetization plateau, where exotic quantum states, including topological ones, are expected to emerge. Here we report the magnetization of a recently discovered kagome QSL candidate YCu_{3}(OH)_{6.5}Br_{2.5} up to 57 T. Above 50 T, a clear magnetization plateau at 1/3 of the saturation moment of Cu^{2+} ions is observed, supporting that this material provides an ideal platform for the kagome Heisenberg antiferromagnet. Remarkably, we found another magnetization plateau around 20 T, which is attributed to the 1/9 plateau. The temperature dependence of this plateau reveals the distinct spin gap, whose magnitude estimated by the plateau width is approximately 10% of the exchange interaction. The observation of 1/9 and 1/3 plateaus highlights the emergence of novel states in quantum spin systems. 
Wednesday, March 6, 2024 8:12AM  8:24AM 
M22.00002: Search for realizations of maple leaf and square kagome Hamiltonians using density functional theory based energy mapping Harald O Jeschke

Wednesday, March 6, 2024 8:24AM  8:36AM 
M22.00003: Everything is a Quantum Ising Model Ruben Verresen Despite being a paragon of manybody quantum physics, the quantum Ising model seems restrictive. In particular, all its interactions are classical (i.e., diagonal in an unentangled basis); indeed, quantum fluctuations only enter through a singlesite term. Nevertheless, this talk will show that how any qudit Hamiltonian (i.e., any lattice model of finitedimensional bosonic degrees of freedom) can arise as the lowenergy description of such an Ising model. At a conceptual level, this uncovers new connections, such as how the spin1/2 Heisenberg model and Kitaev honeycomb model arise from a fourstate Potts model and a fourstate loop model, respectively. We will also see how this universality of Ising models points toward new ways of realizing exotic quantum magnets using minimal ingredients in solid state and cold atom systems. 
Wednesday, March 6, 2024 8:36AM  8:48AM 
M22.00004: OrientationDependent Nuclear Magnetic Resonance (NMR) Studies of Charge Orders in Kagome Superconductors Xiaoling Wang, Arneil P Reyes, Brenden R Ortiz, Stephen D Wilson, Andrea N Capa Salinas AV_{3}Sb_{5} (A=K, Rb, Cs) kagome lattices exhibit both a nonconventional charge density wave (CDW) order (TCDW ∼ 80 − 104 K) and a topological superconducting ground state (TC ∼ 0.9 − 2.5 K).^{17} The CDW state may serve as a precursor to superconductivity, as they can both arise from the same electronic interactions. Consequently, the elucidation of the CDW mechanism in kagome metals assumes significant importance in unraveling the underlying fundamental mechanisms governing their unconventional superconductivity. We employed orientationdependent ^{51}V single crystal nuclear magnetic resonance (NMR) experiments on to investigate the superstructural deformation of the crystal lattice associated with CDW in A=Cs variant. This analysis involves the derivation of anisotropic Knight shift (K) and electric field gradient (EFG) tensors, both highly sensitive to structural transitions and modulations of the electronic charge density caused by CDW. Our examination of the temperaturedependent evolution of K and EFG tensors for ^{51}V reveals particular modes of structural distortion occurring below CDW transition consistent with synchrotron xray diffraction and is in accordance with theoretical calculations. Other indications regarding the charge inhomogeneity associated with charge orders in kagome lattices will be discussed. 
Wednesday, March 6, 2024 8:48AM  9:24AM 
M22.00005: Fractional (and conventional) excitations on the kagome lattice Invited Speaker: Francesco Ferrari As a pivotal model for frustrated magnetism, the kagome lattice antiferromagnet serves as a theoretical platform for exploring different states of spin systems, from conventional magnetic phases to more exotic quantum spin liquids, and their distinctive static and dynamical properties. In this talk, we discuss the characteristic spectral features of different phases on the kagome lattice, computing the dynamical structure factor by means of a variational method based on projected parton wave functions [1]. On the one hand, we study the effect of the DzyaloshinskiiMoriya interaction, highlighting the strong renormalization of magnon modes and the presence of peculiar features in the continuum, which cannot be captured within a linearspin wave approximation [2]. On the other hand, we focus on the chiral spin liquid phase stabilized by threespin interactions [3] and/or longrange couplings [4], which constitute a (bosonic) lattice version of the fractional quantum Hall state [5]. Within this phase, we probe the existence and stability of chiral edge modes in the presence of open boundaries. 
Wednesday, March 6, 2024 9:24AM  9:36AM 
M22.00006: Phase diagram of the KitaevΓ model on the honeycomb lattice Yang Yang, Panagiotis Peter Stavropoulos, Ioannis Rousochatzakis, Natalia Perkins Spin1/2 KΓ model emerges as the minimal description for many Kitaev materials. Despite much effort, the parameter region of K<0 and Γ>0, which is particularly relevant to real materials, remains enigmatic in both quantum and classical models. Hence, in this work, we focus on studying this parameter region both classically and quantummechanically. In the classical limit, we employ Monte Carlo simulations on a series of elongated clusters to show the existence of multisublattice states characterized by scalar chirality. In the quantum limit, we use linkedcluser expansions to show that the quantum ground state can be understood in terms of particular dimer coverings, in a large part of the studied region. We also study the quantum phase diagram with exact diagonalization on the clusters with different sizes and shapes, and show that the results from linkedcluster expansions and from exact diagonalization are consist. 
Wednesday, March 6, 2024 9:36AM  9:48AM 
M22.00007: Twodimensional nonlinear spectroscopy as a probe for frustrated magnets with strong spinorbit coupling Emily Z Zhang, Yong Baek Kim Twodimensional (2D) terahertz spectroscopy has emerged as a powerful technique for probing the nonlinear interactions present in condensed matter systems. Unlike neutron scattering methods, which often require large sample sizes for sufficient momentum space resolution, optical spectroscopy offers a distinct advantage by enabling investigations on smaller samples, especially when large single crystals are unavailable. Moreover, 2D spectroscopy can delineate between the nonlinear interactions that remain concealed within linear response techniques, allowing us to distinguish between nonlinear effects and fractionalizationinduced phenomena. Here, we calculate the nonlinear responses of various frustrated magnets with strong spin orbit coupling, including the generalized Kitaev model. We present the unique signatures exhibited by these systems, shedding light on their responses in both magnetically ordered states, as well as classical and quantum spin liquid states. 
Wednesday, March 6, 2024 9:48AM  10:00AM 
M22.00008: Noncollinear magnetism from frustrated bonddependent anisotropic exchange on the felectron hyperhoneycomb lattice in βNa_{2}PrO_{3} Ryutaro Okuma, Kylie J MacFarquharson, Roger D Johnson, David J Voneshen, Pascal Manuel, Radu Coldea The cooperative magnetism on honeycomb lattices has been recently much explored in search for unconventional magnetic orders or topological Kitaev quantum spin liquid physics predicted for strongly anisotropic exchanges between spinorbit entangled magnetic moments. Whilst most research so far has focused on (transition metal) iridates and ruthenates, rareearth ions have also been theoretically proposed as candidates to host such physics, but are experimentally largely unexplored due to major challenges in materials synthesis. We have successfully synthesized both powders and single crystals of a polymorph of Na_{2}PrO_{3}, with Pr Kramers ions arranged in a hyperhoneycomb lattice, which shares the same local threefold coordination as the planar honeycomb but where additional bond rotations make it a fully threedimensional structure, much studied theoretically as a potential host for unconventional magnetism. Through neutron powder diffraction we reveal a noncollinear magnetic structure, and using inelastic neutron scattering we observe a rich spectrum with strongly dispersive magnetic excitations above a substantial spin gap. Those observations cannot be accounted for by conventional isotropic spin exchanges, but can arise naturally from the cooperative effect of frustrated anisotropic exchanges. Our results highlight that rareearth ions such as 4f Pr^{4+} could provide an important platform, next to 4d Ru^{3+} and 5d Ir^{4+}, for exploring novel forms of cooperative quantum magnetism of spinorbit entangled magnetic moments. 
Wednesday, March 6, 2024 10:00AM  10:12AM 
M22.00009: Theory of moiré magnetism in twisted bilayer αRuCl_{3} Muhammad Akram, Jesse Kapeghian, Jyotrish Das, Roser Valentí, Antia S Botana, Onur Erten We present a comprehensive theory of the longrange ordered magnetic phases of twisted bilayer αRuCl3 via a combination of first principles calculations and atomistic simulations. While a monolayer exhibits zigzag antiferromagnetic order with three possible ordering wave vectors, moir ́e superlattices show a single domain (1q1q) zigzag order with different wave vectors on each layer for large twist angles. For small twist angles, the ground state involves a combination of all three wave vectors (3q3q) in a complex hexagonal domain structure. The multidomain order minimizes the interlayer energy while enduring the energy cost due to the domain wall formation. Comparing these two effects, we obtain an analytical estimate for the critical angle for the transition from 1q to 3q that is in agreement with atomistic simulations. At intermediate angle, we obtain a 2q domain structure on each layer that accommodates both effects. Our results indicate that magnetic frustration due to stackingdependent interlayer exchange in moir ́e superlattices can be used to tune the magnetic ground state and enhance quantum fluctuations in αRuCl3. 
Wednesday, March 6, 2024 10:12AM  10:24AM 
M22.00010: Topological transitions in the site diluted YaoLee spinorbital model Natalia Perkins, WenHan Kao, Vladislav Poliakov The YaoLee (YL) model is an example of exactly solvable spinorbital models that are generalizations of the original Kitaev model with extra local orbital degrees of freedom. 
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