Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session R48: Frustrated Magnetism: KagomeFocus

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Sponsoring Units: GMAG DMP Chair: Haidong Zhou, University of Tennessee, Knoxville Room: 395 
Thursday, March 16, 2017 8:00AM  8:12AM 
R48.00001: Scalar Chiral order on Kagome Antiferromagnet $\rm{Nd_3Sb_3 Mg_2O_14}$ Allen Scheie, Marisa Sanders, Jason Krizan, Akito Sakai, Yosuke Matsumoto, Yiming Qiu, Andrew Christianson, Satoru Nakatsuji, Bob Cava, Collin Broholm We report the magnetic structure of rare earth kagome compound $\rm{Nd_3Sb_3 Mg_2O_14}$. Thermodynamic measurements show a CurieWeiss temperature of CW = −0.12 K, a Nd$^{3+}$ spin1/2 Kramers doublet ground state, and a secondorder phase transition at $T_N$ = 0.56(2) K. Neutron scattering reveals noncoplanar scalar chiral k = 0 longrange magnetic order with an ordered moment of $1.79(5)\mu_B$. This order includes a canted ferromagnetic component perpendicular to the kagome planes, which we have confirmed through low T magnetization measurements. We also report the crystal field levels of $\rm{Nd_3Sb_3 Mg_2O_14}$ and infer the ground state doublet wave function. [Preview Abstract] 
Thursday, March 16, 2017 8:12AM  8:24AM 
R48.00002: Signatures of Dirac cones in a DMRG study of the Kagome Heisenberg model YinChen He, Michael P. Zaletel, Masaki Oshikawa, Frank Pollmann The antiferromagnetic spin$1/2$ Heisenberg model on a kagome lattice is one of the most paradigmatic models in the context of spin liquids but yet the precise nature of its ground state is not understood. We use large scale density matrix normalization group simulations (DMRG) on infinitely long cylinders and find indications for the formation of a gapless Dirac spin liquid. First, we demonstrate using adiabatic flux insertion that the spin gap is much smaller than estimated from previous DMRG simulation. Second, we find that the momentum dependent excitation spectrum extracted from the transfer matrix exhibits Dirac cones that perfectly matches the ones found for a $\pi$flux free fermion model (the parton meanfield ansatz of a $U(1)$ Dirac spin liquid). [Preview Abstract] 
Thursday, March 16, 2017 8:24AM  8:36AM 
R48.00003: Absence of Superconductivity in Doping Kagome Quantum Spin Liquid Thomas Devereaux, Hongchen Jiang, Shenxiu Liu, Steve Kivelson We study the effects of doping a Mott insulator on the kagome lattice where spins interact via antiferromagnetic Heisenberg couplings. This model is known to have a quantum spin liquid ground state at halffilling. The effect of hole doping is studied within the context of the tJ model using largescale densitymatrix renormalization group. Surprisingly, we find that there is no longrange superconductivity in the ground states of the system although the spinspin correlations remain shortranged for doping concentrations up to 11\%. The effective interaction between doped holes is repulsive. The ground states have robust longrange charge density wave order, which is either unidirectional stripe or twodimensional Wigner crystal, whose pattern depends on the lattice geometry and hole doping concentration. These results may be relevant to kagome lattice Herbertsmithite ZnCu3(OH)6Cl2 upon doping. [Preview Abstract] 
Thursday, March 16, 2017 8:36AM  8:48AM 
R48.00004: Tunable Quantum Spin Liquidity in Mo3O13 Cluster Mott Insulators Arash AkbariSharbaf, Djamel Ziat, Aime Verrier, Jeffrey A. Quilliam, Ryan Sinclair, Haidong D. Zhou, Xuefeng F. Sun A study of a tunable quantum spin liquid (QSL) phase in the compound Li$_{\mathrm{2}}$In$_{\mathrm{1}}_{x}$Sc$_{x}$Mo$_{\mathrm{3}}$O$_{\mathrm{8}}$ ($x =$ 0.2, 0.4, 0.6, 0.8, 1) will be presented. Crystal structure of these compounds can be viewed as Mo ions arranged on an asymmetric Kagome lattice (KL),$^{\mathrm{1}}$ with two different MoMo bond lengths, separated by nonmagnetic layers composed of Li, In, and Sc ions. Using Xray diffraction spectroscopy, muon spin relaxation spectroscopy, bulk magnetic susceptibility and specific heat measurements we show that by changing the composition of the nonmagnetic layers we can drive the system from an ordered antiferromagnetic state to a quantum spin liquid state. The mechanism responsible for the tunability of the magnetic phase in this class of materials may be associated with the degree of asymmetry of the KL controlled by the composition of the nonmagnetic layers. For high degree of asymmetry the constraint on the electronic distribution leads to a configuration of Mo$_{\mathrm{3}}$O$_{\mathrm{8}}$ clusters with net spin1/2 per cluster arrange on a triangular lattice$^{\mathrm{2}}$ and long range antiferromagnetic order.$^{\mathrm{3}}$ For low degree of asymmetry the electronic distribution leads to a magnetic phase with QSL character. [1] G. Chen \textit{et al}., arXiv:1408.1963v2 (2014). [2] J. P. Sheckelton \textit{et al}., Nature Mat. 11, 493 (2012). [3] Y. Haraguchi et al., Phys. Rev. B 92, 014409 (2015). [Preview Abstract] 
Thursday, March 16, 2017 8:48AM  9:00AM 
R48.00005: Gapped spin liquid with $\mathbb{Z}_2$topological order for kagome Heisenberg model JiaWei Mei, JiYao Chen, Huan He, XiaoGang Wen We apply symmetric tensor network state (TNS) to study the nearest neighbor spin1/2 antiferromagnetic Heisenberg model on kagome lattice. We keep track of the global and gauge symmetries in TNS update procedure and in tensor renormalization group (TRG) calculation. We use imaginarytime evolution to obtain the variational ground state, and use symmetric TRG to compute the modular matrices. We find that the ground state is a gapped spin liquid with the $\mathbb{Z}_2$topological order (or toric code type). The correlation length is about 10 unit cell length. [Preview Abstract] 
Thursday, March 16, 2017 9:00AM  9:12AM 
R48.00006: Damped Topological Magnons in the Kagom\'{e}Lattice Ferromagnets Alexander Chernyshev, Pavel Maksimov We demonstrate that interactions can substantially alter the freeband description of magnons in ferromagnets on geometrically frustrated lattices. The anharmonic coupling facilitated by the DzyaloshinskiiMoriya interaction and a highlydegenerate structure of the twoparticle continuum induce a nonperturbative damping of the highenergy magnon modes. We provide a detailed account of the effect for the $S\!=\!1/2$ ferromagnet on the kagom\'e lattice and propose further experiments. [Preview Abstract] 
Thursday, March 16, 2017 9:12AM  9:24AM 
R48.00007: Classical Chiral Antiferromagnet on a Kagome Lattice Jackson Pitts, Kirill Shtengel Extensive groundstate degeneracy in classical spin systems has motivated the study of these systems' quantum counterparts in search of topological phases of matter. But the possibility of entropic groundstate selectionorderbydisorderhas also motivated the study of these systems in their own right. Among these is the kagome Heisenberg antiferromagnet (KHAFM) whose low$T$ classical phase exhibits coplanar order. Like the KHAFM, the socalled ``kagome chiral model'' whose interactions are defined by the scalar triple product of neighboring spins has a large classical groundstate degeneracy. Furthermore, the two groundstate manifolds exhibit remarkable similarity, but linear spinwave analysis reveals crucially differing dynamics. All coplanar KHAFM groundstates are equivalent at harmonic order and have flat bands, but the kagome chiral model admits flat bands only for certain states among its analogous ``triaxial'' groundstates: The only zero modes of the kagome chiral model are zero to all orders. Although this undoes the standard argument for orderbydisorder, the set of groundstates having the greatest number of zero modes forms a $Z_2$ spin liquid which may be stabilized by other means. [Preview Abstract] 
Thursday, March 16, 2017 9:24AM  9:36AM 
R48.00008: Tunable Algebraic Correlations on a Kagome Lattice Alexandra Turrini, Patrik Henelius, Peter Holdsworth, Tom Fennell Application of a moderate magnetic field along the $[1 1 1]$ direction of a pyrochlore spin ice such as Ho$_2$Ti$_2$O$_7$ results in a magnetization plateau known as kagome ice. In kagome ice, the three dimensional spin ice physics of the pyrochlore lattice (Coulomb phase, monopole excitations, and Pauling entropy) is confined to a stack of kagome lattices, resulting in a quasitwodimensional Coulomb phase with algebraic spin correlations, modified ice rules, and restricted residual entropy. The kagome ice spin configurations map to the honeycomb dimer model originally studied by Kasteleyn, in which an unconventional phase transition was predicted as a consequence of modifying dimer activity on different families of links. In kagome ice, this effect should be achieved by tilting the magnetic field to modify the degeneracy of the spin configurations. A universal scaling of the algebraic correlations as they are tuned toward the transition as a function of field, temperature, or tilt is predicted, and the tuning is manifested by the drifting of features in the structure factor as any of these control parameters are modified. We investigate the scaling behavior using polarized neutron diffuse scattering measurements. [Preview Abstract] 
(Author Not Attending)

R48.00009: Multimagnon bound states in a 2D system of coupled frustrated ferromagnetic chains Edward Parker, Leon Balents In strong applied fields, ferromagnetic spin chains with a frustrating antiferromagnetic nextnearestneighbor interaction are known to have exotic ``spinnematic'' ground states described by a Luttinger liquid of Bosecondensed {\it bound states} of two or more magnons. These ground states have nontrivial composite order parameters, reflecting the fact that the $U(1)$ spin symmetry about the applied field is not broken all the way down to the identity. We numerically study the stability of these magnon bound states when these chains are coupled into a twodimensional kagom\'{e} lattice (resulting in a spatially anisotropic Hamiltonian that may describe the material $\text{Cu}_3\text{V}_2\text{O}_7(OH)_2 \cdot 2\text{H}_2\text{O}$ (volborthite)). We find that even very weak (although nonzero) couplings cause the magnon pairs to unbind, suggesting that this exotic magnon paircondensation may be difficult to realize in higher than one dimension. [Preview Abstract] 
Thursday, March 16, 2017 9:48AM  10:00AM 
R48.00010: Effect of interaction between fractional excitations on J1J2J3 Ising model on a kagome lattice Tomonari Mizoguchi, Masafumi Udagawa, Ludovic D. C. Jaubert In quantum spin liquids (QSLs), elementary excitations are fractionalized, e.g., the spins are separated into spinons and fluctuating gauge fields. The fractional excitations reflect the nature of QSLs, and a full understanding of their character is awaited. Nevertheless, they are usually approximated as free particles, and we still have little understanding of the essential many body effects of fractional excitations. In this regard, classical spin liquids (CSLs) provide a good stage to study interacting fractional excitations, which have many in common with QSL's. For instance, in classical spin ice, interactions between monopoles give rise to their recombination and alter their dynamical properties. It is plausible to expect similar nontrivial effects will be found in other CSLs. In this presentation, we show the equilibrium properties of the $J_1$$J_2$$J_3$ Ising model on a kagome lattice, in which the fartherneighbor interactions ($\propto J_2=J_3$) is translated into the shortrange interaction between the fractional charges. We will report that the recombination of charges leads to the new CSLs. In one of the new CSLs, the magnetic structure factor shows a ¥lq ¥lq halfmoon" pattern instead of pinch points, which may provides a clue to looking for this new CSL. [Preview Abstract] 
Thursday, March 16, 2017 10:00AM  10:12AM 
R48.00011: Abstract Withdrawn

Thursday, March 16, 2017 10:12AM  10:24AM 
R48.00012: Electron Doping a Kagome Spin Liquid Zachary Kelly, Miranda Gallagher, Tyrel McQueen In 1987, Anderson proposed that charge doping a material with the “resonating valance bond” (RVB) state would yield a superconducting state. Ever since, there has been a search for these RVB containing spin liquid materials and their charge doped counterparts. Studies on the most promising spin liquid candidate, Herbertsmithite, ZnCu$_3$(OH)$_6$Cl$_2$, a two dimensional kagom\'{e} lattice, show evidence of fractionalized excitations and a gapped ground state. In this work, we report the synthesis and characterization of a newly synthesized electron doped spin liquid, ZnLi$_x$Cu$_3$(OH)$_6$Cl$_2$ from $x$ = 0 to $x$ = 1.8 ($3/5$th per Cu$^{2+}$). Despite heavy doping, the series remains insulating and the magnetism is systematically suppressed. We have done extensive structural studies of the doped series to determine the effect of the intercalated atoms on the structure, and whether these structural differences induce strong localization effects that suppress the metallic and superconducting states. Other doped spin liquid candidates are also being explored to understand if this localization is system dependent or systemic to all doped spin liquid systems. [Preview Abstract] 
Thursday, March 16, 2017 10:24AM  10:36AM 
R48.00013: Theory of quantum kagome ice and vison zero modes YiPing Huang, Michael Hermele We derive an effective $Z_2$ gauge theory to describe the quantum kagome ice (QKI) state that has been observed by Carrasquilla \textit{et. al.} in Monte Carlo studies of the $S = 1/2$ kagome XYZ model in a Zeeman field. The numerical results on QKI are consistent with, but do not confirm or rule out, the hypothesis that it is a $Z_2$ spin liquid. Our effective theory allows us to explore this hypothesis and make a striking prediction for future numerical studies, namely that symmetryprotected vison zero modes arise at lattice disclination defects, leading to a Curie defect term in the spin susceptibility, and a characteristic $(N_{dis}  1) \ln 2$ contribution to the entropy, where $N_{dis}$ is the number of disclinations. Only the $Z_2$ Ising symmetry is required to protect the vison zero modes. This is remarkable because a unitary $Z_2$ symmetry cannot be responsible for symmetryprotected degeneracies of local degrees of freedom. We also discuss other signatures of symmetry fractionalization in the $Z_2$ spin liquid, and phase transitions out of the $Z_2$ spin liquid to nearby ordered phases. [Preview Abstract] 
Thursday, March 16, 2017 10:36AM  10:48AM 
R48.00014: Lowenergy theory of the spin$1/2$ Heisenberg antiferromagnet on the Kagome strip Amir MAghaei, Ryan V. Mishmash, Bela Bauer, Kirill Shtengel We study the ground state properties of the spin$1/2$ Heisenberg antiferromagnet on the Kagome strip, a quasi1D ladder of cornersharing triangles. We use the density matrix renormalization group (DMRG) to explore the phase diagram numerically by calculating several physical quantities, including the energy gap, entanglement entropy, and various spin and bond correlation functions. In the fully frustrated regime of our model, we find a gapless state characterized by powerlaw decaying correlation functions at incommensurate wavevectors. Guided by this observation, we analytically consider a twoband system of fermionic spinons coupled to a U(1) gauge field using Bosonization. This approach suggests a potentially stable twoband spin Bose metal (SBM) phase, as well as other possible phases derived from its instabilities. Furthermore, we construct variational wavefunctions inspired by this theory and measure physical observables using variational Monte Carlo (VMC). The VMCDMRG agreement indicates that the twoband SBM is a good starting point to understand the lowenergy physics of the Kagome strip antiferromagnet. [Preview Abstract] 
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