Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session E37: Kagome LatticesFocus

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Sponsoring Units: GMAG DCMP DMP Chair: Jeffrey Quilliam, Universite de Sherbrooke Room: BCEC 206A 
Tuesday, March 5, 2019 8:00AM  8:12AM 
E37.00001: NMR Investigation of the Breathing Kagome Lattice in Li_{2}In_{1x}Sc_{x}Mo_{3}O_{8} Aimé Verrier, Mariam ElAmine, Xavier BazierMatte, Haidong Zhou, Ryan P Sinclair, Jeffrey Quilliam We report ^{7}Li NMR measurements on Li_{2}In_{1x}Sc_{x}Mo_{3}O_{8} at concentrations x=0, 0.6 and 1. The results are compared with those of other groups on the end members of the series [1] and with previous work using muon spin rotation (µSR) [2]. The sample dependence and the effects of pressure on the NMR spectra and on the temperature dependence of the spinlattice relaxation will be discussed, as well as their implications for possible spinon excitations in the spin liquid regime at intermediate Sc concentration. 
Tuesday, March 5, 2019 8:12AM  8:24AM 
E37.00002: Thermal transport properties of S = 1/2 Cdkapellasite Masatoshi Akazawa, Hayato Doki, Kaori Sugii, Masaaki Shimozawa, Minoru Yamashita, HyunYong Lee, Naoki Kawashima, Ryutaro Okuma, Zenji Hiroi, Jung Hoon Han In recent years the thermal Hall effect has gained a great interest as an important signature of the topology. This effect has been observed in paramagnetic phase of kagome antiferromagnets, volborthite and Cakapellasite [1]. These thermal Hall conductivities (κ_{xy}) are shown to be well reproduced by Schwingerboson mean field theory by tuning the DzyaloshinskiiMoriya interaction D and the exchange energy J as fitting parameters. In this talk, we report further evidence supporting the agreement between the experiment and theory from thermal Hall measurements in Cdkapellasite CdCu_{3}(OH)_{6}(NO_{3})_{2 }H_{2}O which has a smaller J/k_{B} ~ 45 K than that of Cakapellasite. We find not only that κ_{xy} of Cdkapellasite is also well reproduced by the theory, but also that the peak temperature in κ_{xy} is shifted to a lower temperature with a larger value in κ_{xy} as expected by the theory. The good scaling of these kagome materials strongly indicates that a kagome antiferromagnet has a common thermal Hall effect of the kagome spins. [1]H. Doki, M. Akazawa, H. Y. Lee et al., Phys. Rev. Lett. 121, 097203 (2018). 
Tuesday, March 5, 2019 8:24AM  8:36AM 
E37.00003: Structural Phase Transitions in the S=1/2 Kagome Antiferromagnets Barlowite and Claringbullite Alyssa Henderson, Lianyang Dong, Sananda Biswas, Hannah I Revell, Yan Xin, John Schlueter, Roser Valenti, Theo Siegrist Barlowite (Cu4(OH)6FBr) and claringbullite (Cu4(OH)6FCl) are atacamite minerals related to the quantum spin liquid (QSL) candidate herbertsmithite ZnCu3(OH)6Cl2, the popular S = ½ antiferromagnet with a geometrically perfect kagome lattice. The kagome lattices of claringbullite and barlowite are stacked perfectly on top of one another and show promise as QSL candidates. Experiments suggest that at room temperature both materials have a hexagonal crystal structure with P6_{3}/mmc symmetry and undergo temperaturedependent phase transitions. Abinitio density functional theory calculations were performed to explain these structural phase transitions. The transitions are likely influenced by the presence of defects, so it is expected that the transition temperature varies from sample to sample and will be different for crystals grown by different methods. 
Tuesday, March 5, 2019 8:36AM  9:12AM 
E37.00004: Interplay of charge and spin degrees of freedom in Mo3O13 cluster Mott insulators Invited Speaker: Arash AkbariSharbaf A promising approach to understanding the complexities of experimental quantum spin liquid candidates is to search for a way to tune the microscopic Hamiltonian and study changes in the resulting magnetic phases. In this talk I will present recent developments in a new class of highly tunable Mo_{3}O_{13} cluster Mott insulators. This family of materials can be viewed as a breathing kagome lattice (BKL) of Mo ions, where the cornersharing up and down triangles have two different sizes. In the compounds Li_{2}In_{1x}Sc_{x}Mo_{3}O_{8} the breathing parameter (λ) changes nonmonotonically with Sc concentration (x), tuning the system from an antiferromagnetic Mott insulator for large λ, to a quantum spin liquid for small λ [1]. For large breathing parameter electrons become confined on the small triangles forming spin1/2 Mo_{3} clusters on a triangular lattice with antiferromagnetic exchange coupling between them, leading to long range antiferromagnetic order. On the other hand, for small breathing parameter electrons are no longer confined to individual Mo_{3} clusters but can tunnel between adjacent clusters, leading to a novel long range plaquette charge order (PCO) [2]. Our thermodynamic and muon spin rotation (μSR) measurements, suggest that the PCO coincides with a high degree of spin frustration and leads to a quantum spin liquid ground state, with gapless spinon excitations. The tunability of these materials can be extended to lower and higher breathing parameter in several related Mooxide materials, revealing additional quantum spin liquids and even ferromagnetism. 
Tuesday, March 5, 2019 9:12AM  9:24AM 
E37.00005: Pressure and doping effects on the lowfield anomalous magnetism in kagome Co_{3}Sn_{2}S_{2} HungCheng Wu, PoJung Sun, DongJie Hsieh, D Chandrasekhar Kakarla, ChingWu Chu, HungDuen Yang Polycrystalline samples Co_{3}Sn_{2}S_{2+x} (0 ≤ x ≤ 0.34) and (Co_{1x}M_{x})_{3}Sn_{2}S_{2.26} (M = Ni and Fe, 0 ≤ x ≤ 0.05) have been synthesized using solidstatereaction and characterized by Xray diffraction (XRD) and electron probe microanalyzer (EPMA). Basically, we are able to reproduce the phase diagram (socalled A phase) as previously reported with negligible sample dependent effect. Furthermore, following the similar procedure and analysis, a socalled A' phase within phase can be sketched in HT phase diagram of Co_{3}Sn_{2}S_{2}. Under the effects of external highpressure and chemical substitutions, the anomalous magnetisms (A and A' ) in low magnetic field show a significant change. The possible origin of the fieldinduced A' phase could be ascribed to the noncollinear skyrmionlike phenomena. These striking findings provide a new candidate in spinfrustrated systems to explore the complexity of magneticfieldinduced magnetism. 
Tuesday, March 5, 2019 9:24AM  9:36AM 
E37.00006: Spin dynamics in the antiferromagnetic Heisenberg model on a pyrochlore slab Preetha Saha, Depei Zhang, GiaWei Chern Unconventional magnetic states such as spin liquids and spin glasses continue to attract the interest of researchers in magnetism. Recently, considerable effort has been focused on understanding their dynamical signatures [12]. We present our study on deterministic spin precession dynamics using energy conserving LandauLifshitz equation on a geometrically frustrated magnet. The lattice constitutes of a triangular arrangement of bipyramids with classical antiferromagnetic Heisenberg interaction. Such a lattice structure is realized in frustrated SrCr_{9}Ga_{129}pO_{19} [SCGO(p)] compounds [3]. Monte Carlo simulations are used to thermalize the system, which is then used as the initial state for the dynamical studies. We explore the temperature, wave vector and frequency dependence in the dynamical structure factor and the corresponding time dependent correlation functions of the model. Dynamics simulations is further used to estimate the extent to which transport of spin excitations in the lattice conform with phenomenological concept of spin diffusion. 
Tuesday, March 5, 2019 9:36AM  9:48AM 
E37.00007: Chiral superconductivity with full Bogoliubov Fermi surface in a doped Kagome spinliquid state. Fan Yang, Yifan Jiang, Hong Yao We employ a largescale variational MonteCarlo simulation to investigate the lightly doped tJ model on the Kagome lattice. We propose several new variational states which smoothly connect to the previously studied uniform 0flux or U(1) $\pi$flux states. By comparing the energies of a variety of trailstates at several systemsizes, we find that the state with lowest energy is a chiral superconducting state with full Bogoliubov Fermi surface, which can be analogous to the FuldeFerrellLarkinOvchinnikov state. The physical properties of this new state and the experimental consequences of the existence of Bogoliubov Fermi surface in this superconducting state are discussed. 
Tuesday, March 5, 2019 9:48AM  10:00AM 
E37.00008: A singlelayer infinite projected entangledpair state study of the chiral antiferromagnetic Heisenberg model on Kagome lattice Reza Haghshenas, Donna Sheng, Shoushu Gong In this talk, we present the study of the chiral antiferromagnetic Heisenberg model on Kagome lattice by using the infinite projected entangledpair state ansatz. We discuss how to develop an efficient optimization algorithm in the framework of the singlelayer tensor network with reduced computation cost O(D^9), where D is the socalled bond dimension of local tensors. We show that the algorithm is stable, providing accurate results similar to previous doublelayer tensor network ansatz. We compare the extracted phase diagram with previous DMRG study and additionally show that only for strong chrial couplings the correlation length, extracted from the transfer matrix, reaches a fixed value for the largest bond dimensions, representing a gaped chiral state. 
Tuesday, March 5, 2019 10:00AM  10:12AM 
E37.00009: Magnetic clustering in frustrated Heisenberg magnets Tomonari Mizoguchi, Ludovic Jaubert, Roderich Moessner, Masafumi Udagawa Fractionalization is one of the fundamental properties of magnets with nontrivial topological character. For example in spin ice, fractionalized degrees of freedom take the form of magnetic monopoles which serve as elementary excitations with a conserved quantum number, their magnetic charge. Recently, it has been pointed out that the clustering of such topological charges leads to characteristic patterns in static structure factors, which we named half moons, distinct form the pinch points that serve as indicators of a Coulomb phase. 
Tuesday, March 5, 2019 10:12AM  10:24AM 
E37.00010: Phases of the ChiralHeisenberg Kagome Antiferromagnet Jackson Pitts, Finn Buessen, Roderich Moessner, Simon Trebst, Kirill Shtengel The ground state degeneracy of the classical kagome Heisenberg antiferromagnet (KHAFM) is remarkably similar to that of the kagome chiral model (KCM) whose Hamiltonian consists of the scalar spin chiralities on the triangles of the lattice. However, models containing both types of interactions have reduced degeneracies. If chiral terms are introduced uniformly, the √3×√3 state lifts from the ground state manifold, but if they are introduced with staggered sign, the q=0 state is excluded instead. Only once the Heisenberg terms are entirely eliminated are states of both types again ground states. This has drastic effects on the orderbydisorder mechanism that drives coplanar ordering in the KHAFM. Our Monte Carlo simulations demonstrate a more discriminating selection effect in the intermediate models. Furthermore, even in the case of the pure KCM, only the √3×√3 structure is observed. We explain this by counting the soft modes of the KCM’s ground states. Only states of √3×√3 structure have sufficient populations of soft modes to drive the system to order. Due to an extra degeneracy of the KCM this structure exists on a large set of states forming a classical spin liquid. 

E37.00011: ABSTRACT WITHDRAWN

Tuesday, March 5, 2019 10:36AM  10:48AM 
E37.00012: Temperature dependence of butterfly effect in a classical manybody system Thomas Bilitewski, Subhro Bhattacharjee, Roderich Moessner We study the chaotic dynamics in a classical manybody system of interacting spins on the kagome lattice. We characterise manybody chaos via the butterfly effect as captured by an appropriate outoftimeordered commutator. Due to the emergence of a spin liquid phase, the chaotic dynamics extends all the way to zero temperature. We thus determine the full temperature dependence of two complementary aspects of the butterfly effect: the Lyapunov exponent, μ, and the butterfly speed, vb, and study their interrelations with usual measures of spin dynamics such as the spindiffusion constant, D and spinautocorrelation time, τ. We find that they all exhibit power law behaviour at low temperature, consistent with scaling of the form D∼v_{b}^{2}/μ and τ^{1}−T. The vanishing of μ∼T^{0.48} is parametrically slower than that of the corresponding quantum bound, μ∼T, raising interesting questions regarding the semiclassical limit of such spin systems. 
Tuesday, March 5, 2019 10:48AM  11:00AM 
E37.00013: A mechanism for thermal Hall effect in Mott insulating spin liquid Yonghao Gao, Gang Chen We study the origin of thermal Hall effect from the spinon transport in a U(1) spinon metal. The external magnetic field, that polarizes the spins, effectively generates an internal U(1) gauge flux for the spinons and twists the spinon motion through the antisymmetric interaction. Such a mechanism for Lorentz force generation differs fundamentally from the induction of the internal U(1) gauge flux in the weak Mott insulating regime from the charge fluctuations. We apply this understanding to the specific cases of spinon metals in Kagome lattice and hyperkagome lattice. We carry out a numerical calculation of the thermal Hall conductivity within the linear response theory and discuss the relevance with the thermal transport measurement in Kagome materials volborthite and kapellasite. 
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