Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Q51: Quantum Spin Liquid IIIFocus Recordings Available
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Sponsoring Units: GMAG DCMP Chair: Shangshun Zhang, University of Minnesota Room: McCormick Place W-474B |
Wednesday, March 16, 2022 3:00PM - 3:12PM |
Q51.00001: Determination of spin Hamiltonian for an ideal triangular lattice of Yb in NaBaYb(BO3)2 Alireza Ghasemi, Anirudha Menon, Shu Gao, Collin L Broholm, Robert J Cava, Rajiv R Singh, Natalia Drichko In the search for materials with a quantum spin liquid phase, the triangular lattice of Yb is of interest. Frustration combined with the ability of the Kramers ion Yb3+ to form a pseudo spin-1/2 degree of freedom, may provide favorable conditions for a quantum spin liquid. Here we study NaBaYb(BO3)2, which contains high quality triangular layers of Yb3+. One layer is sandwiched between two layers of Na+, the other between two layers of Ba2+. Low temperature heat capacity measurements indicate the inter-site interactions are in the same range as magnetic dipole interactions [1]. Here we determine the Hamiltonian that describes the low temperature magnetism of NaBaYb(BO3)2. We used Raman Spectroscopy and Inelastic Neutron Scattering to determine the crystal field level scheme and the ground state wavefunction for Yb3+.The Numerical Linked Cluster method was used to analyze the low field thermodynamic data and obtain estimates for the inter-site interactions. |
Wednesday, March 16, 2022 3:12PM - 3:24PM |
Q51.00002: The case for a U(1)π Quantum Spin Liquid Ground State in the Dipole-Octupole Pyrochlore Ce2Zr2O7 Evan M Smith, Owen M Benton, Danielle R Yahne, Benedikt Placke, Jonathan Gaudet, Jérémi Dudemaine, Avner Fitterman, James W Beare, Andrew R Wildes, Suvam Bhattacharya, Timothy N DeLazzer, Connor Buhariwalla, Nicholas Butch, Roman Movshovich, James Garrett, Casey Marjerrison, James P Clancy, Edwin Kermarrec, Graeme M Luke, Andrea Bianchi, Kate A Ross, Bruce D Gaulin The Ce3+ pseudospin-½ degrees of freedom in the pyrochlore magnet Ce2Zr2O7 are known to possess dipole-octupole character, making it a candidate for novel quantum spin liquid ground states at low temperatures. We’ve measured the heat capacity of Ce2Zr2O7 and fit the result to a quantum numerical linked cluster (NLC) calculation that allows estimates for the terms in the near-neighbour XYZ Hamiltonian expected for such dipole-octupole pyrochlore systems. Fits of the same theory to the temperature dependence of the magnetic susceptibility and unpolarized neutron scattering complement this analysis to produce robust estimates of the near-neighbour exchange parameters. A comparison between the resulting best fit NLC calculation and new polarized neutron diffraction results shows agreement, as well as discrepancies which are attributed to interactions beyond near-neighbours, such as zone-boundary diffuse scattering in the non-spin flip channel. We conclude that Ce2Zr2O7 realizes a U(1)π quantum spin liquid state at low temperatures, and one that resides near the boundary between dipolar and octupolar character. |
Wednesday, March 16, 2022 3:24PM - 3:36PM |
Q51.00003: Low-temperature quantum magnetism of the frustrated magnet LiYbSe2 Olivia Vilella
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Wednesday, March 16, 2022 3:36PM - 3:48PM |
Q51.00004: Field-Induced Spin Dynamics of the S = 1/2 Triangular-Lattice Antiferromagnet CsYbSe2 Tao Xie, Jie Xing, Stanislav Nikitin, Satoshi Nishimoto, Manuel Brando, Pavlo Khanenko, Joerg Sichelschmidt, Liurukara D Sanjeewa, Athena S Sefat, Andrey Podlesnyak Geometrically frustrated magnets provide an intriguing playground for investigation of novel phenomena in condensed matter physics. Strong magnetic frustration may produce large degeneracy of the ground state and prevent formation of magnetic order in favor of exotic states such as quantum spin-liquid or spin-ice phases. The two-dimensional (2D) triangular-lattice antiferromagnet is a prototypical example of a frustrated antiferromagnet, and thus is a good platform to explore potential quantum spin-liquid behavior. We will present the recent in-field neutron scattering study examining a 2D spin-1/2 triangular-lattice antiferromagnet, CsYbSe2, which is a member of the large family of rare-earth chalcogenide quantum spin liquid candidates. The inelastic neutron scattering spectra evolve from highly damped continuum-like excitations at zero field to relatively sharp spin wave modes in the field-induced up-up-down phase. The density-matrix renormalization group calculations with a Heisenberg triangular-lattice nearest-neighbor antiferromagnetic model reproduce the essential features of the experimental spectra, including continuum-like excitations at zero field, a series of sharp magnons in the up-up-down phase as well as higher energy two-magnon excitations. This work presents a comprehensive experimental and theoretical overview of the unconventional field-induced spin dynamics in triangular-lattice Heisenberg antiferromagnets. |
Wednesday, March 16, 2022 3:48PM - 4:00PM |
Q51.00005: Specific heat of the kagome antiferromagnet herbertsmithite in high magnetic fields Quentin Barthélemy, Albin Demuer, Christophe Marcenat, Thierry Klein, Bernard Bernu, Laura Messio, Matias Velázquez, Edwin Kermarrec, Fabrice Bert, Philippe Mendels Herbertsmithite ZnCu3(OH)6Cl2 is an emblematic quantum spin liquid candidate because it is the closest materialization of the nearest neighbor S = ½ kagome Heisenberg antiferromagnet (J ∼ 190 K) with a dynamical ground state. As main perturbations, we can mention copper ions on the zinc sites between the kagome planes and a finite out-of-plane Dzyaloshinskii-Moriya component (Dz ∼ 0.06J). |
Wednesday, March 16, 2022 4:00PM - 4:12PM |
Q51.00006: Quantum Spin Liquid with Emergent Chiral Order in the Triangular-lattice Hubbard Model Andreas Weichselbaum, Bin-Bin Chen, Wei Li, Ziyu Chen, Shou-Shu Gong, Donna Sheng The interplay between spin frustration and charge fluctuation gives rise to an exotic quantum state in the intermediate-interaction regime of the half-filled triangular-lattice Hubbard (TLU) model, while the nature of the state is under debate. Using the density matrix renormalization group with SU(2)spin U(1)charge symmetries implemented, we study the TLU model defined on long cylindrical geometries. Here we discuss our current progress on the gapped chiral Kalmeyer-Laughlin quantum spin liquid encountered in the TLU at intermediate onsite interaction 9 < U / t < 10.75 in between the metallic and the antiferromagnetic Mott insulating phases. |
Wednesday, March 16, 2022 4:12PM - 4:24PM |
Q51.00007: Emergent parastatistical quasiparticles in exactly solvable lattice spin models Zhiyuan Wang, Kaden R Hazzard Parastatistics is one of the few alternatives to the usual fermion and boson statistics. Parastatistical particles transform in higher dimensional representations of the permutation group under particle exchange, and satisfy generalized Pauli exclusion principles. While their existence as elementary particles has been ruled out by a no-go theorem [1] in relativistic quantum field theory, in this talk I show that they can emerge as emergent quasiparticles in a family of parity-time-symmetric quantum lattice spin models. This family of models can be exactly solved using a generalized Jordan-Wigner transformation, which transforms the spin operators into paraparticle creation and annihilation operators satisfying generalized quadratic commutation relations. (Note: This is very different from the notion of parafermions [2], which don’t form higher dimensional representation of the permutation group.) The single particle spectra are the same as certain lattice free fermion systems, but the paraparticles satisfy generalized Pauli exclusion principles, i.e. the same state can hold up to n paraparticles, where n is a constant integer. The models can exhibit several interesting phase transitions, including a band insulator-conductor- topological insulator transition, where the critical exponents can be exactly calculated. |
Wednesday, March 16, 2022 4:24PM - 4:36PM |
Q51.00008: TMDs as a platform for spin liquid physics: A strong coupling study of twisted bilayer WSe2 Dominik Kiese The advent of twisted moire heterostructures as a playground for strongly correlated electron physics has led to a plethora of experimental and theoretical efforts seeking to unravel the nature of the emergent superconducting and insulating states. Amongst these layered compositions of two dimensional materials, transition metal dichalcogenides (TMDs) are by now appreciated as highly-tunable platforms to simulate reinforced electronic interactions in the presence of low-energy bands with almost negligible bandwidth. Here, we focus on the twisted homobilayer WSe2 and the insulating phase at half-filling of the flat bands reported therein. More specifically, we explore the possibility of realizing quantum spin liquid (QSL) physics on the basis of a strong coupling description, including up to second nearest neighbor Heisenberg couplings J1 and J2, as well as Dzyaloshinskii-Moriya (DM) interactions. Mapping out the global phase diagram as a function of an out-of-plane displacement field, we indeed find evidence for putative QSL states, albeit only close to SU(2) symmetric points. In the presence of finite DM couplings and XXZ anisotropy, long-range order is predominantly present, with a mix of both commensurate and incommensurate magnetic phases. |
Wednesday, March 16, 2022 4:36PM - 5:12PM |
Q51.00009: Second generation of triangular spin-liquid candidates Invited Speaker: Alexander Tsirlin Recent years have seen an increased interest in studying the spin-liquid physics of triangular antiferromagnets. On the experimental side, YbMgGaO4 was the first and very successful shot, but its spin-liquid-like ground state is strongly influenced by the Mg/Ga disorder and associated randomness. In this talk, I will review the results on the second generation of spin-liquid candidates that were recently introduced as disorder-free triangular antiferromagnets. I will show that, despite the initial claims, Na2BaCo(PO4)2 is magnetically long-range-ordered below 150 mK and reveals subtle randomness effects caused by structural dynamics. An extensive mapping of the temperature-field phase diagram suggests a close proximity of this compound to the nearest-neighbor XXZ triangular antiferromagnet. Further on, I will present thermodynamic properties of the AYbX2 (A = Na, K and X = S, Se) rocksalt-type compounds where a competition between first- and second-neighbor interactions on the triangular lattice may stabilize the spin-liquid state. I will discuss the nature of low-energy excitations in these materials as well as their possible quantum critical behavior. |
Wednesday, March 16, 2022 5:12PM - 5:24PM |
Q51.00010: Ferromagnetism and Spin Liquid Behavior in [Mo3]11+ Molecular Magnets Jeffrey A Quilliam, Qiang Chen, Arash Akbari-Sharbaf, Aime Verrier, Ryan P Sinclair, Zhiling Dun, Qing Huang, Haidong Zhou, Adam A Aczel, Redha Rouane, Martin P Mourigal, Eun Sang Choi, Jiaqiang Yan Molecular magnets based on [Mo3]11+ units with one unpaired electron per trimer have attracted recent interest due to the identification of quantum spin liquid candidacy in the family member LiZn2Mo3O8. Here, we present comprehensive measurements on polycrystalline samples of the three related systems ZnScMo3O8, MgScMo3O8, and Na3Sc2Mo5O16 with the same Mo3O13 magnetic building blocks. The crystal structures are characterized with powder x-ray diffraction and the magnetic ground states are determined by performing AC and DC susceptibility, specific heat, neutron powder diffraction, and μSR measurements. Our work indicates that ZnScMo3O8 and MgScMo3O8 are weak ferromagnets, with zero field ordering temperatures of TC ~ 6 K and TC<1.5 K respectively. On the other hand, Na3Sc2Mo5O16 hosts a dynamical magnetic ground state and therefore is a candidate for quantum spin liquid behavior. By comparing the present results to past work on the same family of materials, we construct a universal phase diagram for this family of materials which suggests that their magnetic ground states are very sensitive to subtle changes in the nearest-neighbor Mo-Mo distance. |
Wednesday, March 16, 2022 5:24PM - 5:36PM |
Q51.00011: Magnetic correlations in the semimetallic hyperkagome iridate Na3Ir3O8: a rare case of doping in a quantum spin liquid Philippe Mendels, Gediminas Simutis, Tomohiro Takayama, Quentin Barthélemy, Fabrice Bert, HIDENORI TAKAGI A decade ago the first realization of an effective spin 1/2 hyper-kagome lattice was discovered in the form of Na4Ir3O8, which is an insulator and was found to exhibit spin freezing at ~7 K . |
Wednesday, March 16, 2022 5:36PM - 5:48PM |
Q51.00012: Complete breakdown of magnons in the square lattice iridate Sr2IrO4 Jinkwang Kim, Hoon Kim, Hyun Woo Kim, Jimin Kim, Jungho Kim, Bumjoon Kim Quantum (spin-1/2) Heisenberg antiferromagnet on a square lattice is a main building block of cuprate high-temperature superconductors, and its magnetism can mostly be explained by the semi-classical spin-wave theory. However, a pronounced deviation from the spin-wave theory is observed at a certain momentum—also known as (π, 0) anomaly—in the magnetic excitation spectra of cuprates. The single magnon spectral weight is significantly reduced and transferred to an isotropic high-energy continuum, which has been interpreted as a precursor of spinon deconfinement transition. Here, we revisit the magnetic excitation spectra of the single-layer iridate Sr2IrO4 using resonant inelastic x-ray scattering. With a judicious selection of a scattering geometry and a small domain aligning magnetic field, we resolve the transverse and longitudinal responses, and reveal a completely isotropic magnetic spectrum at (π,0), indicating a zero spectral weight for a single-magnon pole. This result correlates with a much steeper spin-wave dispersion along the magnetic zone boundary and thus suggests that a large ring exchange interaction is responsible for the complete breakdown of magnons, signaling a nearby quantum critical point. |
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