Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session R36: New Examples of Quantum Spin LiquidInvited

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Sponsoring Units: GMAG Chair: Sara Haravifard, Duke Univ Room: BCEC 205C 
Thursday, March 7, 2019 8:00AM  8:36AM 
R36.00001: 1TTaS2 as a 45 year old spin liquid. Invited Speaker: Patrick Lee

Thursday, March 7, 2019 8:36AM  9:12AM 
R36.00002: Evidence for a quantum spin liquid in singlelayer 1TTaSe_{2} Invited Speaker: Wei Ruan Quantum spin liquids are a novel state of matter predicted to arise in quantum antiferromagnets where magnetic frustration or quantum fluctuations are strong enough to prevent magnetically ordered states even down to the lowest temperatures. Quantum spin liquids are believed to exist in strongly correlated Mott insulators, and are thus related to unconventional superconductivity. Much work on quantum spin liquids has focused on triangular and kagome lattices where frustration is strong. An example is the bulk Mott insulator 1TTaS_{2} which has attracted attention as a quantum spin liquid candidate due to localized dorbitals in the Ta atoms that form a triangular lattice in this material. This scenario, however, is complicated by interlayer coupling and possible different stacking orders in the bulk, thus motivating investigation into related singlelayer materials. 
Thursday, March 7, 2019 9:12AM  9:48AM 
R36.00003: Halfinteger thermal quantum Hall effect in a Kitaev spin liquid: A signature of Majorana edge modes and nonAbelian excitations Invited Speaker: Yuichi Kasahara Kitaev quantum spin liquid (QSL) displays the fractionalization of quantum spins into Majorana fermions. In magnetic fields, the emergence of Majorana edge current is predicted to manifest itself in the form of thermal quantum Hall effect. Here we report on thermal Hall conductivity κ_{xy} measurements in αRuCl_{3}, a candidate material for Kitaev QSL on twodimensional (2D) honeycomb lattice. In magnetic field perpendicular to the 2D honeycomb planes, positive κ_{xy} develops in a spinliquid state below the temperature characterized by the Kitaev interaction J_{K}/k_{B} ∼80 K, demonstrating the presence of highly unusual itinerant excitations. Although the zerotemperature property is masked by the magnetic ordering at T_{N} = 7 K, the sign, magnitude, and Tdependence of κ_{xy} at T_{N}< T < J_{K}/k_{B} follows the predicted trend of the itinerant Majorana fermion excitations. The application of a tilted magnetic field suppresses the AFM order, leading to a fieldinduced QSL ground state. In this QSL state, the 2D thermal Hall conductance per honeycomb plane κ_{xy}^{2D}/T shows a plateau behavior as a function of applied magnetic field and has a quantization value of π^{2}k_{B}^{2}/6h, which is exactly half of κ_{xy}^{2D}/T in the integer quantum Hall state and fractional quantum Hall state that hosts Abelian anyons. This halfinteger thermal Hall conductance provides direct evidence of a nonAbelian phase and topologically protected chiral edge modes of charge neutral Majorana fermions (particles that are their own antiparticles), which have half degrees of freedom of conventional fermions. Above a critical field, the quantization disappears and κ_{xy}^{2D}/T goes to zero rapidly, indicating a topological phase transition. 
Thursday, March 7, 2019 9:48AM  10:24AM 
R36.00004: Numerical Studies of Quantum Spin Liquids in Kitaev and Heisenberg Models Invited Speaker: Donna Sheng Rapid advancement in largescale numerical simulations for strongly correlated systems has led to great progress 
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