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: Spin-liquids 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 triangular-lattice antiferromagnetic nearest-neighbor 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 tirangular-lattice Hubbard model in the vicinity of the Mott transition hosts a chiral spin-liquid (CSL) state spontaneously breaking time-reversal symmetry. However, past literature studying an effective SU(2) invariant spin Hamiltonian derived from a strong-coupling 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 density-matrix 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 time-reversal 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: Ba3NiIr2O9: a three-dimensional 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 Ba3NiIr2O9, which suits our expectations. Here both Ni and Ir ions are magnetically active and form a 2D frustrated triangular lattice. X-ray absorption spectroscopy measurements confirm the presence of Ni2+ (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 µ-SR measurements. Ab-initio calculations find a strong magnetic exchange between Ir and Ni sublattices and in-plane 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 spin-chain arrays Eyal Leviatan, David F. Mross We introduce a lattice spin-1/2 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 spin-chain 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 four-spin 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 3d7 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 spin-liquid-like 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: 1T-TaS2 as a quantum spin liquid: from bulk to atomically-thin layers. Samuel Mañas-Valero, Eugenio Coronado Layered materials are excellent candidates for studying the interplay between the in-plane and out-of-plane entanglement in strongly correlated systems. A relevant example is provided by 1T-TaS2, 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 out-of-plane 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 Z2 quantum spin liquids on the simple cubic, body centered cubic, and face centered cubic lattices using a spin-rotation-invariant fermionic projective symmetry group approach. Taking into account that all three lattices share the same point group Oh, 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 short-range mean-field models for the fermionic partons (spinons) these phases collapse to only very few relevant cases. We finally present self-consistently calculated spinon band dispersions for the face centered cubic lattice up third nearest-neighbor couplings and discuss the relation of a network of symmetry-protected 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 pressure-induced gapped spin-liquid ground state in a coupled ladder antiferromagnet C9H18N2CuBr4 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 spin-1/2 coupled ladder antiferromagnet C9H18N2CuBr4 (DLCB for short). In DLCB, the inter-ladder coupling is sufficiently strong to drive the system to the long-range antiferromagnetic ordering phase below TN=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 single-crystal heat capacity and neutron diffraction measurements suggets that the magnetic order breaks down above a critical pressure Pc~1.0 GPa. By contrasting with quantum Monte Carlo calculations of the dynamic structure factor, the follow-up inelastic neutron scattering above Pc reveals evidence of a Z2 spin-liquid phase in terms of characteristic fully gapped vison-like 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 spin-conserving U(1) spin liquids. This interaction shifts the two-spinon continuum up in energy and leads to the appearance of the collective spin-1 mode in the transverse dynamic susceptibility at small momenta. This general effect is checked by detailed analytical and numerical calculations for the best-understood spin liquid — the spin-1/2 magnetized Heisenberg chain. We show that antiferromagnetic next-nearest neighbor exchange interaction can be used to tune the spin chain between the interacting spinon liquid and non-interacting spinon gas regimes at a small magnetic field. We describe how the Dzyaloshinskii-Moriya interaction can be used to detect the interaction-induced splitting of transverse spin modes at small momentum in the ESR experiments. |
Tuesday, March 16, 2021 1:54PM - 2:06PM Live |
F39.00009: Spin-orbit 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 long-range 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 spin-anisotropic frustrated magnet FeI2 Xiaojian Bai, Shang-Shun 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 well-defined magnon excitations. Exotic magnetic fluctuations with fractional, topological or multipolar character, have been proposed for unconventional forms of magnetic matter such as spin-liquids. As a result, considerable efforts have searched for, and uncovered, low-spin materials with suppressed dipolar order at low temperatures. Long-range order of magnetic dipoles, however, is much more common. Here, we report neutron-scattering experiments and quantitative theoretical modeling of a spin-1 system – the uniaxial triangular magnet FeI2 – where a dispersive band of mixed dipolar-quadrupolar fluctuations with large spectral-weight emerges just above a dipolar ordered ground-state. This excitation arises from anisotropic exchange interactions that hybridize overlapping modes carrying fundamentally different quantum numbers. A generalization of spin-wave theory to local SU(3) degrees of freedom accounts for all details of the low-energy 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 ferro-antiferromagnetic Rb2Cu2Mo3O12 Shohei Hayashida, Lysander Huberich, Daniel Flavian Blasco, Zewu Yan, Kirill Povarov, Severian Gvasaliya, Andrey Zheludev The linear chain molybdate Rb2Cu2Mo3O12 is one of the most intriguing species among linear quantum ferro-antiferromagnets. 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 Rb2Cu2Mo3O12 using single crystal samples. |
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