Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session H24: 2D Frustrated Spin Systems: Kagome and HoneycombFocus

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Sponsoring Units: GMAG DMP Chair: Alexander Chernyshev, Univ of California  Irvine Room: LACC 403A 
Tuesday, March 6, 2018 2:30PM  2:42PM 
H24.00001: Phase diagram of the stuffed honeycomb lattice Jyotisman Sahoo, Dmitrii Kochkov, Bryan Clark, Rebecca Flint We introduce the stuffed honeycomb lattice (honeycomb lattice with a superimposed triangular lattice formed by sites at the center of each hexagon) that interpolates between the triangular and the honeycomb lattice. The triangular lattice limit is particularly interesting as DMRG results indicate a clear spin liquid(SL) region whose nature is still unclear. The classical phase diagram has a multicritical point on the triangular lattice axis, with two new neighboring phases appearing only off axis. Both phases have free classical angles that allow both chiral and nonchiral configurations, with orderbydisorder selecting the nonchiral phases. The quantum phase diagram found via exact diagonalization hosts a large SL region that eats up most of the phase space of the new classical phases; we will present a symmetry analysis of the possible nature of the spin liquids in this region. 
Tuesday, March 6, 2018 2:42PM  2:54PM 
H24.00002: Emergent Chiral Spin State in the Mott Phase of a Bosonic KaneMeleHubbard Model Kirill Plekhanov, Ivana Vasic, Alexandru Petrescu, Rajbir Nirwan, Guillaume Roux, Walter Hofstetter, Karyn Le Hur Recently, the frustrated XY model for spins1/2 on the honeycomb lattice has attracted a lot of attention in relation with the possibility to realize a chiral spin liquid state. This model is relevant to the physics of some quantum magnets. Using the flexibility of ultracold atoms setups, we propose an alternative way to realize this model through the Mott regime of the bosonic KaneMeleHubbard model. The phase diagram of this model is derived using the bosonic dynamical meanfield theory. Focussing on the Mott phase, we investigate its magnetic and topological properties as a function of frustration using exact diagonalization and bosonic dynamical meanfield theory. We do find an emergent chiral spin state in the intermediate frustration regime. This gapped phase displays a chiral order, breaking spontaneously timereversal and parity symmetry, but its Chern number is zero. 
Tuesday, March 6, 2018 2:54PM  3:06PM 
H24.00003: Short range order in the quantum XXZ honeycomb lattice material γBaCo2(PO4)2 Harikrishnan Nair, Jesse Brown, Ethan Coldren, Gavin Hester, Martin Gelfand, Andrei Podlesnyak, Kate Ross γBaCo_{2}(PO_{4})_{2} (γBCPO) is a honeycomblattice compound with quasitwodimensional structure exhibiting shortrange ordered (SRO) frustrated magnetism. We have studied hydrothermally synthesized γBCPO samples via magnetometry (Χ_{ac}), specific heat (C_{p}), x ray and inelastic neutron scattering (INS) experiments. Χ_{ac} and C_{p} showed a broad anomaly at ∼ 5 K, with two weak kink features in C_{p} at T_{N1} ∼ 6 K and T_{N2} ∼ 3.5 K. Collinear antiferromagnetic SRO with ordering wavevector k_{c} = 0.5 and correlation length ξ_{c} = 60 Å and quasi2D helical SRO with k_{h} = 0.25 and ξ_{h} = 253 Å form below T_{N1} and T_{N2} respectively. Our INS data compares well with linear spin wave theory for two separate parameter regimes of the XXZ J_{1}J_{2}J_{3} model with near neighbor ferromagnetic exchange, J_{1}. Competing further interactions, J_{2} and J_{3} place γBCPO near regions of high classical degeneracy such as the highly frustrated point, J_{1}/2 = J_{2} = J_{3}. Our analysis suggests that γBCPO balances near the edge of competing classical phases of the XXZ J_{1}J_{2}J_{3} model, implying that frustration and quantum fluctuations may account for its inability to form a long range order state. 
Tuesday, March 6, 2018 3:06PM  3:18PM 
H24.00004: Electronic transport in Layered van der Waals Kagome lattice Cluster Compound, Nb_{3}X_{8} Jiho Yoon, Edouard Lesne, John Sheckelton, Chris Pasco, Tyrel McQueen, Stuart S Parkin, Mazhar Ali Geometrically frustrated materials based on a Kagome lattice have been long studied as promising “Quantum SpinLiquid” candidates. Of particular interest are metallic spin liquids – theorized to host exotic transport properties including high temperature superconductivity. Recently, the 2D van der Waals cluster compound, Nb_{3}Cl_{8}, which has a Nb Kagome lattice, has been reported as a potential spin liquid material. Due to its insulating behavior, electronic transport properties and their link to the exotic magnetism have not been investigated. Here we report on electronic transport measurements in 10nm100nm thin flakes of Nb_{3}X_{8} (X= Cl, Br) in Hall bar geometries, fabricated via standard micromechanical exfoliation techniques combined with photolithography and ionsputtering deposition. Also, results on using electrostatic charge injection via backgate and topgate control to metallize the compound and probe a possibly metallic spin liquid state will be presented. 
Tuesday, March 6, 2018 3:18PM  3:30PM 
H24.00005: Quantum Spin Liquid with Even Ising Gauge Field Structure on Kagome Lattice Yancheng Wang, XueFeng Zhang, Frank Pollmann, Meng Cheng, ZiYang Meng Employing largescale quantum Monte Carlo simulation, we study the extended XXZ model on kagome lattice. A $\mathbb Z_2$ quantum spin liquid phase with effective even Ising gauge field structure emerges from the delicate balance among three symmetry breaking phases including stripe solid, staggered solid and ferromagnetic phase. This $\mathbb Z_2$ spin liquid is beyond the LiebSchultzMattisOshikawaHastings theorem and made possible by the introduction of an extended interaction related to RokhsarKivelson potential. The phase transitions from staggered solid to spin liquid and ferromagnetic phase are first order, so is the transition between stripe solid and ferromagnetic phase. However, the transition between spin liquid and ferromagnetic phase is found to be continuous and belong to 3D XY$^*$ universality class associated with the condensation of spinons, and the transition between spin liquid and stripe solid is seemingly continuous and associated with the condensation of visons. 
Tuesday, March 6, 2018 3:30PM  3:42PM 
H24.00006: Barlowite: The next quantum spin liquid? Christopher Pasco, Ivo Heinmaa, Ravio Stern, Collin Broholm, Tyrel McQueen Barlowite, Cu_{4}(OH)_{6}BrF, is a newly reported quantum spin liquid (QSL) host material, containing “perfect” kagomé layers separated by interlayer Cu^{2+} ions, with reports that Zn^{2+} substitution for Cu^{2+} induces a QSL ground state. In this talk, we will report on the crystal growth and a comprehensive suite of measurements, including xray and neutron diffraction, NMR, specific heat, and magnetization that resolve the ambiguities of the previously reported disorder on the interlayer sites, and provide a quantitative comparison of the physics of Barlowite to other synthetic Cu^{2+} kagomé minerals. These results pave the way to discovery of S=1/2 kagomé realizations with minimal interlayer coupling effects. 
Tuesday, March 6, 2018 3:42PM  3:54PM 
H24.00007: Perpendicular susceptibility and geometrical frustration of twodimensional kagomé Ising antiferromagnet Mahfuza Khatun, Khandker Muttalib, Jeremiah Barry We present perpendicular susceptibility of antiferromagnetic kagomé Ising model obtained from the exact solutions of localized evennumber correlations. The susceptibility is calculated with nearestneighbor pair interactions where strong frustration prevents longrange ordering and with triplet (threespin) interactions which has no frustration but the system remains disordered down to T=0 temperature. At the zero temperature limit the perpendicular susceptibility for the nearestneighbor interaction model diverges while it is constant in the triplet interaction model. Both models with and without frustrations show finite residual entropy at the zero temperature limit. Finally, these results are compared with the susceptibilities of twodimensional kagomé ferromagnetic [1] and triangular antiferromagnetic Ising models. Our findings suggest that the perpendicular susceptibility can be a measure of the degree of frustration of twodimensional Ising spin systems[2]. 
Tuesday, March 6, 2018 3:54PM  4:06PM 
H24.00008: Quantum Spin Liquid in a Distorted Kagome Lattice and the Pyrochlore Lattice Li Ern Chern, Kyusung Hwang, Tomonari Mizoguchi, Yejin Huh, Robert Schaffer, Sopheak Sorn, YongBaek Kim The Kagomelatticebased material, volborthite, has been considered as a promising platform for the discovery of exotic quantum ground states. Using projective symmetry group (PSG) analysis and Schwinger boson mean field theory, we explore the possible quantum spin liquid (QSL) and magnetically ordered phases in a twodimensional nonsymmorphic lattice described by the plane crystallographic group p2gg [1], which is consistent with the spatial anisotropy of the spin model of volborthite derived from density functional theory. We find that the QSL ground state is related to a coplanar incommensurate spiral order, while a closely competing QSL state is related to a spin density wave order. In addition, periodicity enhancement of the two spinon spectrum is observed in the competing QSL state as a result of symmetry fractionalization. Finally, we discuss the correspondence between the bosonic and fermionic QSL states through vison PSG [2]. 
Tuesday, March 6, 2018 4:06PM  4:18PM 
H24.00009: Electron Doping of Proposed Kagome Quantum Spin Liquid Produces Localized Electrons in Band Gap States but Not Free Electrons Qihang Liu, Tyrel McQueen, Stephan Lany, Alex Zunger Cu_{3}ZnX with X=[(OH)_{6}Cl_{2}] or X=[(OH)_{6}BrF] are Kagome Heisenberg antiferromagnets that display some of the expected quantum spin liquid (QSL) fingerprints, creating the hope that electron doping would enable the long sought hightemperature superconductivity. However, successful insertion of electrons does not necessarily mean free electrons with the ensuing shifted Fermi energy. Z. Kelly et al. recently found that insertion of as much 0.6 Li ions per Cu^{2+ }into Cu_{3}Zn[(OH)_{6}Cl_{2}] does not show the expected metallic conductivity. We have used the modern theory of doping to enquire what happens to electrons inserted into such lattices, particularly the possible interplay between local structural disorder and localization tendencies. Using approaches that correct the selfinteraction error we find that whereas the d^{9} electrons of Cu^{2+} in the undoped Cu_{3}Zn(OH)_{6}BrF are spread over a broad energy range inside the valence band, upon adding an electron, this broad distribution of levels is bunched into a narrow range of highly localized d^{10} states inside the band gap. This suggests that the CuX manifold has an intrinsic tendency to localize added electrons into a polaronic state. 
Tuesday, March 6, 2018 4:18PM  4:30PM 
H24.00010: Gapless SpinLiquid Ground State in the S=1/2 Kagome Antiferromagnet HaiJun Liao, ZhiYuan Xie, Jing Chen, ZhiYuan Liu, HaiDong Xie, RuiZhen Huang, Bruce Normand, Tao Xiang The defining problem in frustrated quantum magnetism, the ground state of the nearestneighbor S = 1/2 antiferromagnetic Heisenberg model on the kagome lattice, has defied all theoretical and numerical methods employed to date. We apply the formalism of tensornetwork states, specifically the method of projected entangled simplex states, which combines infinite system size with a correct accounting for multipartite entanglement. By studying the groundstate energy, the finite magnetic order appearing at finite tensor bond dimensions, and the effects of a nextnearestneighbor coupling, we demonstrate that the ground state is a gapless spin liquid. We discuss the comparison with other 
Tuesday, March 6, 2018 4:30PM  4:42PM 
H24.00011: Effect of the DzyaloshinskiiMoriya Interactions in the Kagome Heisenberg Antiferromagnet ChihYuan Lee, Bruce Normand, YingJer Kao We investigate the effects of DzyaloshinskyMoriya (DM) interactions in the kagome antiferromagnet by means of projected entangled simplex states (PESS). Our result shows that the critical value of the DM interaction D_{C} between the gapless spin liquid and the Neel state is D/J ≈0.040, which is only half of the magnitude proposed previously and smaller than the value of D in herbertsmithite. Our work implies that there might be other origins of the spin liquid nature in herbertsmithite. 
Tuesday, March 6, 2018 4:42PM  4:54PM 
H24.00012: Signatures of gapless fermionic spinons on a strip of the kagome Heisenberg antiferromagnet Ryan Mishmash, Amir MAghaei, Bela Bauer, Kirill Shtengel Developing a complete understanding of the ground state properties of spin1/2 Heisenberg antiferromagnets on the 2D kagome lattice remains a central challenge in the field of frustrated quantum magnetism. Here, we consider the narrowest possible quasi1D incarnation of the kagome Heisenberg antiferromagnet which consists entirely of cornersharing triangles. Using largescale density matrix renormalization group calculations, we identify in this model an extended gapless quantum phase characterized by central charge c=2 and powerlaw decaying spin and bondenergy correlations which oscillate at tunably incommensurate wave vectors. We argue that this intriguing spin liquid phase can be understood as a marginal instability of a twoband spinon Fermi surface coupled to a U(1) gauge field, an interpretation which we substantiate via bosonization analysis and Monte Carlo calculations on model Gutzwiller variational wave functions. Our results represent one of the first numerical demonstrations of fermionic spinons in a simple SU(2) invariant nearestneighbor Heisenberg model beyond the strictly 1D (Bethe chain) limit. 
Tuesday, March 6, 2018 4:54PM  5:06PM 
H24.00013: Investigation of the anomalous Hall effect in Kagome lattice materials with d and felectrons Nakheon Sung, Filip Ronning, Joe Thompson, Eric Bauer Recently, a large anomalous Hall effect due to magnetic frustration in the Kagome lattice with a noncollinear antiferromagnetic spin arrangement was observed in the Mn_{3}X (X = Ga, Ge, Sn) compounds. The Ni_{3}Sn crystal structure (P6_{3}/mmc) [14] of these materials is regarded as an excellent platform for understanding the mechanism of the anomalous Hall effect and may be a candidate for realizing novel topological phenomena in future memory storage devices or in sensors. It is important to discover and characterize new materials with noncollinear magnetic structures to understand the origin of the nonvanishing Berry curvature that leads to the large anomalous Hall effect. Here, we report the physical properties of novel d and felectron materials with the Ni_{3}Sntype crystal structure. 
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