Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session D51: Quantum Spin Liquid IFocus Recordings Available
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Sponsoring Units: GMAG DCMP Chair: Fazel Tafti, Boston College Room: McCormick Place W-474B |
Monday, March 14, 2022 3:00PM - 3:36PM |
D51.00001: Microscopic Mechanism for a Higher-Spin Kitaev Model Invited Speaker: Panagiotis Peter Stavropoulos Transition metal compounds offer a vast playground for the emergence of unconventional magnetism and novel states like the quantum spin liquid, which can be traced back to bond-dependent interactions like the Kitaev interaction. The microscopic mechanism that brings rise to such interactions is crucial in order to understand their relative strength and how to tune them, which reveals the relevant part of the phase diagram and guides material searches. This has been incredibly successful in studying compounds that form pseudospin 1/2 moments, however, bond-dependent interactions may exist among higher spin S moments as well. In this talk a microscopic mechanism for higher spin S moment models with bond-dependent interactions is presented, where S=1 and S=3/2 cases are addressed explicitly. Possible material candidates that can host this mechanism are also discussed. |
Monday, March 14, 2022 3:36PM - 3:48PM |
D51.00002: Instabilities of spin-one Kitaev Spin Liquid phase in presence of single-ion anisotropies Owen Bradley, Rajiv Singh Recently, several candidates for Kitaev materials with a spin-1 local degree of freedom have been proposed, motivating further study of higher spin Kitaev models. Here we explore the spin-1 Kitaev honeycomb model in the presence of single-ion anisotropies, using exact diagonalization and perturbative techniques. We present results for two types of single-ion anisotropy: a D111 anisotropy which preserves the symmetry between the three bond directions of the honeycomb lattice, and D100 anisotropy which does not. We will show evidence of a phase transition separating the Kitaev Spin Liquid phase from more conventional phases as the magnitude of the D111 anisotropy is varied. The limiting cases of both types of single-ion anisotropy will be discussed, as well as the differences between ferromagnetic and antiferromagnetic Kitaev couplings in this model. |
Monday, March 14, 2022 3:48PM - 4:00PM |
D51.00003: Phase diagram of a bilinear-biquadratic spin-1 model on the triangular lattice from DMRG Aaron Szasz, Chong Wang, Yin-Chen He We investigate a highly frustrated model of spin-1 degrees of freedom on the triangular lattice, with nearest- and next-nearest-neighbor antiferromagnetic S·S interactions and nearest-neighbor (S·S)2 interactions. Using the density matrix renormalization group (DMRG) technique, we find a large variety of phases, including three magnetic orders, spin nematic phases, and at least one disordered phase that may be a spin liquid. |
Monday, March 14, 2022 4:00PM - 4:12PM |
D51.00004: Majorana corner states in square and Kagome quantum spin liquids Alessandro Principi, Haoran Wang Quantum spin liquids hosting Majorana excitations have recently experienced renewed interest for potential applications to topological quantum computation. Performing logical operations with reduced poisoning requires to localize such quasiparticles at specific point of a device, with energies that are well defined and inside the bulk energy gap. These are two defining features of second order topological insulators (SOTIs). Here, we show two spin models that support quantum spin liquid phases characterised by Majorana excitations and that behave as SOTIs, one of which is analytically solvable thanks to a theorem by Lieb. We show that, depending on the values of spin couplings, it is possible to localize either fermions or Majorana particles at their corners. |
Monday, March 14, 2022 4:12PM - 4:24PM |
D51.00005: Finite field dynamics of the dipole-octupole quantum spin liquid pyrochlore Ce2Zr2O7 Anish Bhardwaj, Shu Zhang, Han Yan, Andriy H Nevidomskyy, Hitesh J Changlani We study the physics of the quantum spin liquid (QSL) candidate Ce2Zr2O7 whose magnetic properties emerge from the dipole-octupole nature of the magnetic cerium ions. Its low-energy description is in terms of an effective pseudo spin-1/2 Hamiltonian where only the local z-component of the applied field linearly couples to the local x- and z-component of the spin while the octupolar y-component remains invisible. Using the Hamiltonian we obtained in our previous study [A. Bhardwaj et al.,arXiv:2108.01096] which captures the dynamical features in zero field, we extend our analysis to the case of finite applied magnetic fields. For this purpose, we perform a combination of classical Monte Carlo and Landau-Lifshitz dynamical calculations and Lanczos both at zero and finite temperature. We find that the continuum seen in the dynamical structure factor, consistent with the existence of a gapless QSL, is largely suppressed on the introduction of a magnetic field, giving way to Bragg peaks. However, the absence of any dispersive modes is strongly reflective of the octupolar nature of the low energy modes, a finding that can be directly tested in neutron experiments. |
Monday, March 14, 2022 4:24PM - 4:36PM |
D51.00006: Projective symmetry group analysis of symmetric U(1) and Z2 multipolar quantum spin liquids on the pyrochlore lattice Félix Desrochers, Li Ern Chern, Yong-Baek Kim Multipolar pyrochlore rare-earths magnets form an interesting class of quantum spin liquids (QSLs) candidates. The intrinsic relation between their pseudo-spin degree of freedom and the local crystalline environment may lead to enhanced quantum fluctuations, disorder-promoted QSLs, and novel detection schemes. In this work, we extend the previous projective symmetry group (PSG) classification of Z2 QSLs on the pyrochlore lattice for bosonic spinons by Liu, Halàsz, and Balents [Phys. Rev. B 100, 075125 (2019)] to multipolar QSLs and further determine all U(1) PSG classes. |
Monday, March 14, 2022 4:36PM - 4:48PM |
D51.00007: Flux-gap Renormalization in the Random Kitaev Spin Ladder Wen-Han Kao, Natalia B Perkins The discovery of Kitaev materials and the fact that disorder is inevitable in real samples call for a better understanding of how quenched randomness modifies the quantum spin liquid phase. To address this problem, as a first step we consider disorder effects on the Kitaev spin ladder, where the bonds on the legs (rungs) are covered by alternating x- and y-type (z-type) Ising couplings. Unlike the Kitaev spin chain, plaquette fluxes as conserved quantities can be defined on the ladder. In this talk we present the strong-disorder renormalization group (SDRG) study of Kitaev spin ladder with random interactions. The low-energy physics can be solved perturbatively through the Schrieffer-Wolff transformation. For small Jy, it is similar to the random transverse-field Ising chain (RTIC) where the fixed-point behavior is controlled by Jx and Jz distributions. However, while the pseudo-spin gap is determined by Jx and Jz, the flux gap distribution has additional dependence on Jy. In the extreme-value statistics, we show that in the off-critical region, the pseudo-spin and flux gaps follow the same Griffiths singularity as in RTIC. On the other hand, while the pseudo-spin gap shows the infinite-disorder fixed point at the critical point, the flux gap reveals a different scaling behavior. |
Monday, March 14, 2022 4:48PM - 5:00PM |
D51.00008: A search for spinon echoes in the Ising chain CoNb2O6 Brad D Price, Xiaoling Wang, Mathilde Papillon, Jason W Krizan, Robert J Cava, Tyrel M McQueen, Seyed M Koohpayeh, Norman P Armitage, Mark S Sherwin CoNb2O6, a twisted Kitaev chain, is a promising candidate for observing transverse field Ising chain (TFIC)-like low-energy 1D excitations [1]. The low energy excitations of a TFIC are hypothesized to be topologically-protected fractionalized spin-1/2 quasiparticles, often called ‘spinons’. Spinons must always be excited in pairs and there are many ways to deposit energy and momentum into two particles; this leads to a broad absorption continuum that hides most of the information about spinon lifetimes and lineshapes. Recent theory has predicted that detection of spinon echoes could enable determination of these properties [2]. UCSB's free electron laser-powered pulsed electron magnetic resonance spectrometer has been used to measure spin echoes in various paramagnetic systems at 240 GHz [3,4] and is uniquely positioned to detect spinon echoes. We will present our progress toward measuring spinon echoes in CoNb2O6, from which we are currently able to place an upper bound on spinon lifetimes. |
Monday, March 14, 2022 5:00PM - 5:12PM |
D51.00009: Hydrodynamics of interacting spinons in the magnetized spin-½ chain with the uniform Dzyaloshinskii-Moriya interaction Ren-Bo Wang, Anna Keselman, Oleg A Starykh Elementary excitations of the quantum spin chain are represented by neutral spin-½ spinons. Recently, the magnitude of the marginally irrelevant interaction between spinons was determined from the electron spin resonance (ESR) experiments on the spin-½ chain with the uniform Dzyaloshinskii-Moriya (DM) interaction, subject to the magnetic field oriented along the DM vector. Here, we present a simple hydrodynamic approach to dynamical spin susceptibilities of the interacting spinon liquid that allows us to describe the general case of the arbitrary angle between the magnetic field and the DM vector. The approach is based on the Kac-Moody algebra of spin currents and a simple mean-field approximation that takes into account "molecular" fields due to the backscattering interaction between spinons. The obtained results reproduce the old ones [2] in the limiting cases and are in good agreement with the DMRG simulations. We show that the interaction between spinons influences the angular dependence of the resonant magnetic fields of the DM-induced doublet and compare our theory to the existing ESR data [3], thereby providing additional evidence in favor of the interacting spinon liquid picture. |
Monday, March 14, 2022 5:12PM - 5:24PM |
D51.00010: Field induced spin nematic liquid in the 1D anisotropic quantum spin systems Toru Sakai The spin nematic phase is one of interesting topics in the field of the magnetism. The previous theoretical and numerical studies predicted that the spin nematic order would be induced by the frustration of the ferromagnetic and antiferromagnetic exchange interactions, or the biquadratic interaction. The spin nematic order is characterized by the long-range four spin correlation and the two-magnon bound state. The previous numerical diagonalization study had indicated that a similar two-magnon bound state can occur in the S=1 antiferromagnetic chain with the single-ion anisotropy under magnetic field. The recent calculation of the critical exponents of the spin correlation functions suggested that this two-magnon bound state includes the spin nematic liquid phase, as well as the SDW liquid one. Some phase diagrams with respect to the anisotropy and the magnetization were obtained by the numerical diagonalization of finite size clusters. The same numerical analysis indicated that the spin nematic liquid phase appears in the magnetization process of the 1/2 spin ladder system with the anisotropic ferromagnetic rung interaction. |
Monday, March 14, 2022 5:24PM - 5:36PM |
D51.00011: Field-Theoretic Simulations of Fully-Fluctuating Spin Lattices at Finite Temperature Ethan C McGarrigle, Kris T Delaney, Leon Balents, Henri Orland, Glenn H Fredrickson We explore the equilibrium behavior of quantum spin-1/2 lattice models at finite temperature using approximation-free field-theoretic methods. Other exact methods for simulating spins, such as quantum Monte Carlo or Density Matrix Renormalization Group (DMRG), either crumble under the sign problem inherent to many frustrated spin models or are limited to low site densities and 1D-like geometries, respectively. To overcome these challenges, this work presents a new approach that 1) makes an exact transformation from spins to Schwinger Bosons and 2) leverages our previous numerical framework that uses complex Langevin dynamics to sample fluctuating bosonic coherent states field theories at finite temperature both efficiently and accurately. We apply this approach to fully-fluctuating quantum Heisenberg models and validate our results by comparison with single spin and 1D spin chain references. We display the method’s ability to predict thermodynamic averages at finite temperature and discuss numerical stability limitations. |
Monday, March 14, 2022 5:36PM - 5:48PM |
D51.00012: Excitation spectrum of spin-1 Kitaev spin liquids Yu-Hsueh Chen, Jozef Genzor, Yong-Baek Kim, Ying-Jer Kao We study the excitation spectrum of the spin-1 Kitaev model using the symmetric tensor network. By evaluating the virtual order parameters defined on the virtual Hilbert space in the tensor network formalism, we confirm the ground state is in a $\mathbb{Z}_2$ spin liquid phase. Using the correspondence between the transfer matrix spectrum and low-lying excitations, we find that contrary to the dispersive Majorana excitation in the spin-1/2 case, the isotropic spin-1 Kitaev model has a dispersive bosonic charge anyon excitation. Bottom of the gapped single-particle charge excitations are found at $\mathbf{K}, \mathbf{K}'=(\pm2\pi/3, \mp 2\pi/3)$, with a corresponding correlation length of $\xi \approx 6.7$ unit cells. The lower edge of the two-particle continuum, which is closely related to the dynamical structure factor measured in inelastic neutron scattering experiments, is obtained by extracting the excitations in the vacuum superselection sector in the anyon theory language. |
Monday, March 14, 2022 5:48PM - 6:00PM |
D51.00013: Octupolar correlations and spinon continuum in Ce3+ pyrochlores Victor Porée, Sylvain Petit, Elsa Lhotel, Tom Fennell, Romain Sibille Rare-earth pyrochlore frustrated magnets have played a central role in the study of three- dimensional quantum spin liquids (QSL) over the last years. Recent experimental studies on Ce2Sn2O7 and Ce2Zr2O7 have further boosted the interest in quantum spin ice (QSI) states. Owing to the crystal electric field in pyrochlores, Ce3+ can stabilize a dipole-octupole Kramers ground state doublet. Magnetic measurements do not show any sign of ordering or freezing down to the lowest accessible temperatures but suggest the presence of a correlated ground state. |
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