Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session F39: Spin Liquid IFocus Live

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Sponsoring Units: GMAG DMP Chair: Kate Ross, Colorado State University 
Tuesday, March 16, 2021 11:30AM  11:42AM Live 
F39.00001: Spinliquids on the triangular lattice in a spin model approximating the Hubbard model Taylor Cookmeyer, Johannes Motruk, Joel Ellis Moore The weak ordering tendency of the triangularlattice antiferromagnetic nearestneighbor Heisenberg model has drawn considerable attention to whether additional couplings or degrees of freedom might destabilize the order yielding a quantum spin liquid. Recently, the authors of [Phys. Rev. X 10, 021042 (2020)] provided numerical evidence that the tirangularlattice Hubbard model in the vicinity of the Mott transition hosts a chiral spinliquid (CSL) state spontaneously breaking timereversal symmetry. However, past literature studying an effective SU(2) invariant spin Hamiltonian derived from a strongcoupling expansion reports not a CSL, but other states such as a U(1) spin liquid with spinon Fermi surface. To better understand the competition between these phases in the spin model, we use both exact diagonalization and the infinite densitymatrix renormalization group to characterize the extended phase diagram of the spin Hamiltonian. We find that the CSL is the ground state in a finite parameter region as evidenced by spontaneous timereversal symmetry breaking, a fractionally quantized spin Hall conductivity, and the expected chiral structure of the entanglement spectrum. We comment on the connection to the CSL in the Hubbard model and earlier reported spin liquid states. 
Tuesday, March 16, 2021 11:42AM  11:54AM Live 
F39.00002: Ba_{3}NiIr_{2}O_{9}: a threedimensional spin liquid with two magnetic sublattices Siddharth Kumar, Swarup Panda, Manju Mishra Patidar, Shashank Ojha, Prithwijit Mandal, Gangadhar Das, John Freeland, V Ganesan, Peter J Baker, Srimanta Middey The quantum spin liquid (QSL) is an exotic phase of magnetic materials where the spins continue to fluctuate without any symmetry breaking down to zero temperature. Over the past 15 years, several quantum spin liquid candidates have been proposed with spin – ½ in 2D frustrated lattices. But it is difficult to realize such a state in 3D systems with higher spins as these factors may suppress quantum fluctuations giving ordering in the system. We devised a new strategy to find such candidates by utilizing two magnetically active ions at different crystallographic locations. We have synthesized Ba_{3}NiIr_{2}O_{9}, which suits our expectations. Here both Ni and Ir ions are magnetically active and form a 2D frustrated triangular lattice. Xray absorption spectroscopy measurements confirm the presence of Ni^{2+} (S=1). Absence of any spin ordering/freezing and existence of a gapless QSL state at least down to 100 mK is confirmed by magnetic susceptibility, heat capacity, and µSR measurements. Abinitio calculations find a strong magnetic exchange between Ir and Ni sublattices and inplane antiferromagnetic coupling between the dimers, resulting in dynamically fluctuating magnetic moments on both the Ir and Ni sublattice. 
Tuesday, March 16, 2021 11:54AM  12:06PM Live 
F39.00003: Quantum spin liquids with tunable Fermi surfaces in spinchain arrays Eyal Leviatan, David F. Mross We introduce a lattice spin1/2 model that realizes a U(1) quantum spin liquid with a tunable Fermi surface as its ground state. Using bosonization techniques, we introduce a coupled spinchain model that maps exactly onto a theory of two spinons coupled to an emergent photon. These spinons form a Fermi surface, whose volume can be tuned via the parameters of the microscopic wire model. Finally, we construct a lattice spin Hamiltonian with two and fourspin terms that generate the analyzed wire model. 
Tuesday, March 16, 2021 12:06PM  12:42PM Live 
F39.00004: Design and Synthesis of Quantum Spin Liquid Candidates Invited Speaker: Robert Cava Although materials such as Iridium oxides and the layered form of Ruthenium trichloride have provided the materials physics community with many rich opportunities to study materials whose properties suggest that they are viable quantum spin liquid candidates, an additional family of materials has emerged in this context  the layered Cobalt oxides. Divalent Co has always been an outlier in the periodic table because no matter whether you ascribe its 3d^{7} valence electron count to a low spin or high spin configuration, its effective magnetic moment in oxides is often too large, an indication (to me at least) that the orbital contribution to its effective moment has not been quenched by the ligand field, which is not the case for most of the 3d transition elements. This can give rise to some special magnetic properties and has led to some materials that are reasonable candidates for displaying a spinliquidlike state at low temperatures. We have also found some interesting rare earth oxides in this class, I think. In this talk I will describe some of the materials that my undergrads, grad students and postdocs have found and investigated in this regard. 
Tuesday, March 16, 2021 12:42PM  12:54PM Live 
F39.00005: 1TTaS_{2} as a quantum spin liquid: from bulk to atomicallythin layers. Samuel MañasValero, Eugenio Coronado Layered materials are excellent candidates for studying the interplay between the inplane and outofplane entanglement in strongly correlated systems. A relevant example is provided by 1TTaS_{2}, which shows a multifaceted electronic and magnetic scenario due to the existence of several charge density waves (CDW) configurations, including quantum hidden phases, superconductivity and even quantum spin liquid (QSL) phases, that are highly dependent on the outofplane stacking of the CDW. 
Tuesday, March 16, 2021 12:54PM  1:06PM Live 
F39.00006: Projective symmetry group classifications of quantum spin liquids on the simple cubic, body
centered cubic, and face centered cubic lattices Jonas Sonnenschein We perform extensive classifications of Z_{2} quantum spin liquids on the simple cubic, body centered cubic, and face centered cubic lattices using a spinrotationinvariant fermionic projective symmetry group approach. Taking into account that all three lattices share the same point group O_{h}, we apply an efficient gauge where the classification for the simple cubic lattice can be partially carried over to the other two lattices. We identify hundreds of projective representations for each of the three lattices, however, when constructing shortrange meanfield models for the fermionic partons (spinons) these phases collapse to only very few relevant cases. We finally present selfconsistently calculated spinon band dispersions for the face centered cubic lattice up third nearestneighbor couplings and discuss the relation of a network of symmetryprotected linelike zero modes in reciprocal space with their corresponding projective symmetry group representation. 
Tuesday, March 16, 2021 1:06PM  1:18PM Live 
F39.00007: Evidence for a pressureinduced gapped spinliquid ground state in a coupled ladder antiferromagnet C_{9}H_{18}N_{2}CuBr_{4} Tao Hong, Tao Ying, Qing Huang, Sachith Dissanayake, Yiming Qiu, Mark Turnbull, Andrey Podlesnyak, Yan Wu, Huibo Cao, Izuru Umehara, Jun Gouchi, Yoshiya Uwatoko, Masaaki Matsuda, David A Tennant, Kai Schmidt, Stefan Wessel Here we present a comprehensive study of the effect of hydrostatic pressure on the magnetic structure and spin dynamics in a spin1/2 coupled ladder antiferromagnet C_{9}H_{18}N_{2}CuBr_{4} (DLCB for short). In DLCB, the interladder coupling is sufficiently strong to drive the system to the longrange antiferromagnetic ordering phase below T_{N}=2.0 K [1]. Analysis of the spin Hamiltionian suggests that DLCB is close to the quantum critical point in two dimensions at ambient pressure and zero field [2]. The singlecrystal heat capacity and neutron diffraction measurements suggets that the magnetic order breaks down above a critical pressure P_{c}~1.0 GPa. By contrasting with quantum Monte Carlo calculations of the dynamic structure factor, the followup inelastic neutron scattering above P_{c} reveals evidence of a Z_{2} spinliquid phase in terms of characteristic fully gapped visonlike and fractionalized excitations in the distinct scattering channels. 
Tuesday, March 16, 2021 1:18PM  1:54PM Live 
F39.00008: Collective modes of magnetized spin liquids. Invited Speaker: Oleg Starykh We show that Zeeman magnetic field enhances the interaction between spinons in spinconserving U(1) spin liquids. This interaction shifts the twospinon continuum up in energy and leads to the appearance of the collective spin1 mode in the transverse dynamic susceptibility at small momenta. This general effect is checked by detailed analytical and numerical calculations for the bestunderstood spin liquid — the spin1/2 magnetized Heisenberg chain. We show that antiferromagnetic nextnearest neighbor exchange interaction can be used to tune the spin chain between the interacting spinon liquid and noninteracting spinon gas regimes at a small magnetic field. We describe how the DzyaloshinskiiMoriya interaction can be used to detect the interactioninduced splitting of transverse spin modes at small momentum in the ESR experiments. 
Tuesday, March 16, 2021 1:54PM  2:06PM Live 
F39.00009: Spinorbit coupled heavy metals as a probe of frustrated magnetic systems Vikram Nagarajan, Ella Lachman, Hossein Taghinejad, James Analytis In strongly frustrated magnetic materials, a magnetically ordered state may be suppressed by quantum fluctuations. Such a situation can lead to a quantum spin liquid ground state, where quantum fluctuations a strongly enhanced and lead to longrange entanglement. We realize several experiments to detect signatures of these fluctuations by coupling a magnetically frustrated insulator to an adjacent heavy metal layer. By measuring the evolution of the heavy metal resistivity with temperature and magnetic field, the behavior of these fluctuations can be mapped out. We comment on how our measurements may have relevance to fractional excitations in such systems. 
Tuesday, March 16, 2021 2:06PM  2:18PM Live 
F39.00010: Hybridized quadrupolar excitations in the spinanisotropic frustrated magnet FeI2 Xiaojian Bai, ShangShun Zhang, Zhiling Dun, Hao Zhang, Qing Huang, Haidong Zhou, W. Adam Phelan, Matthew Brandon Stone, Alexander Kolesnikov, Feng Ye, Vasile Garlea, Andrey Podlesnyak, Cristian Batista, Martin P Mourigal Magnetic order is usually associated with welldefined magnon excitations. Exotic magnetic fluctuations with fractional, topological or multipolar character, have been proposed for unconventional forms of magnetic matter such as spinliquids. As a result, considerable efforts have searched for, and uncovered, lowspin materials with suppressed dipolar order at low temperatures. Longrange order of magnetic dipoles, however, is much more common. Here, we report neutronscattering experiments and quantitative theoretical modeling of a spin1 system – the uniaxial triangular magnet FeI2 – where a dispersive band of mixed dipolarquadrupolar fluctuations with large spectralweight emerges just above a dipolar ordered groundstate. This excitation arises from anisotropic exchange interactions that hybridize overlapping modes carrying fundamentally different quantum numbers. A generalization of spinwave theory to local SU(3) degrees of freedom accounts for all details of the lowenergy dynamical response of FeI2 without going beyond quadratic order. Our work highlights that quantum excitations without classical counterparts can be realized even in presence of fully developed magnetic order. 
Tuesday, March 16, 2021 2:18PM  2:30PM Live 
F39.00011: Dielectric properties of the linear quantum ferroantiferromagnetic Rb_{2}Cu_{2}Mo_{3}O_{12} Shohei Hayashida, Lysander Huberich, Daniel Flavian Blasco, Zewu Yan, Kirill Povarov, Severian Gvasaliya, Andrey Zheludev The linear chain molybdate Rb_{2}Cu_{2}Mo_{3}O_{12} is one of the most intriguing species among linear quantum ferroantiferromagnets. Its interesting property is the appearance of magnetoelectric response at temperatures above the onset of magnetic order. This has been interpreted as the emergence of chiral spin liquid state [1]. Recently, we reported the first comprehensive thermodynamic studies on single crystal samples. The entire low temperature magnetic phase diagram was mapped out [2]. We now report the first study of dielectric properties of Rb_{2}Cu_{2}Mo_{3}O_{12} using single crystal samples. 
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