Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session W15: Focus Session: Theory of Kagome Magnetism |
Hide Abstracts |
Sponsoring Units: GMAG DMP Chair: Oleg Tchernyshyov, Johns Hopkins University Room: 317 |
Thursday, March 21, 2013 2:30PM - 2:42PM |
W15.00001: Simplex SU(3) quantum antiferromagnets on the kagome and hyperkagome lattices Yury Yu. Kiselev, Siddharth A. Parameswaran, Daniel P. Arovas We investigate SU(3) ``simplex solid'' antiferromagnets on the kagome and hyperkagome lattices. The ground states of these systems are annihilated by certain local projectors acting on triples of sites, and are analogous to the valence bond solid wavefunctions constructed by Affleck, Kennedy, Lieb, and Tasaki. Using a coherent state representation, we map to a classical model of $CP^2$ spins with 3-spin interactions, which we analyze via single-spin Monte Carlo simulations and a cluster algorithm for the three-body interactions. We compute the static structure factor and short-range correlations encoded by the simplex solid wavefunction and rationalize the results in terms of the ``order by disorder'' mechanism. [Preview Abstract] |
Thursday, March 21, 2013 2:42PM - 2:54PM |
W15.00002: Structure of dynamical correlations developing on top of an entropically designed frustrated manifold Mathieu Taillefumier, Julien Robert, Benjamin Canals, Christopher Henley By combining monte carlo and spin dynamics simulations, we investigate the precessional dynamics of the classical kagome antiferromagnet through the calculation of the dynamical structure factor $S({\bf Q},t)$. Recently, evidences for spin wave like excitations in the two distinct low temperature regimes whose temperature ranges are given by the entropically driven onset of spin plane coplanarity at $T_0/J\approx 5\ 10^{-3}$ has been given. However, only a little is known about the longer time scales describing the fluctuations around the ground-state manifold. We give more insight about this relaxationnal dynamics and establish in particular the temperature and wave-vector dependence of the lifetime of locally ordered states. Although the infinite components spins model qualitatively accounts for the dynamical properties in the cooperative paramagnetic regime, we show at lower temperature that the entropic selection (i) leads to strongly different dynamical correlations for the in- plane and out-of-plane spin components below the transition, and (ii) almost suppresses the diffusive behaviour observed in the cooperative regime in favour of mainly propagative spin transfers. [Preview Abstract] |
Thursday, March 21, 2013 2:54PM - 3:06PM |
W15.00003: DMRG Study of the $S\ge 1$ quantum Heisenberg Antiferromagnet on a Kagome-like lattice without loops R. Zach Lamberty, Hitesh J. Changlani, Christopher L. Henley The Kagome quantum Heisenberg antiferromagnet, for spin up to $S=1$ and perhaps $S=3/2$, is a prime candidate to realize a quantum spin liquid or valence bond crystal state, but theoretical or computational studies for $S>1/2$ are difficult and few. We consider instead the same interactions and $S\ge1$ on the Husimi Cactus, a graph of corner sharing triangles whose centers are vertices of a Bethe lattice, using a DMRG procedure tailored for tree graphs [1]. Since both lattices are locally identical, properties of the Kagome antiferromagnet dominated by nearest-neighbor spin correlations should also be exhibited on the Cactus, whereas loop-dependent effects will be absent on the loopless Cactus. Our study focuses on the possible transition(s) that must occur with increasing $S$ for the Cactus antiferromagnet. (It has a disordered valence bond state at $S=1/2$ but a 3-sublattice coplanar ordered state in the large $S$ limit [2]). We also investigate the phase diagram of the $S=1$ quantum XXZ model with on-site anisotropy, which we expect to have three-sublattice and valence-bond-crystal phases similar to the kagome case [3]. ([1] Changlani et al, arXiv:1208.1773 (2012), [2] Doucot and Simon, J. Phys. A 31, 5855 (1998), [3] Isakov and Kim, Phys. Rev. B 79, 094408 (2009)) [Preview Abstract] |
Thursday, March 21, 2013 3:06PM - 3:18PM |
W15.00004: Wannier Permanents and Featureless Bosonic Mott Insulators on the 1/3 Filled Kagome Lattice Ari Turner, Siddharth Parameswaran, Itamar Kimchi, Dan Stamper-Kurn, Ashvin Vishwanath We study Bose-Hubbard models on tight-binding, non-Bravais lattices, with a filling of one boson per unit cell -- and thus fractional site filling. At integer filling of a unit cell, a fully symmetric insulating state is in principle allowed without triggering topological order. We demonstrate by explicit construction of a family of wavefunctions that such a featureless Mott insulating state exists at 1/3 filling on the kagome lattice. We construct Hamiltonians for which these wavefunctions are exact ground states. Such wavefunctions also yield 1/3 magnetization plateau states for spin models in an applied field. The featureless Mott states we discuss can be generalized to any lattice for which symmetric exponentially localized Wannier orbitals can be found at the requisite filling, and their wavefunction is given by the permanent over all Wannier orbitals. [Preview Abstract] |
Thursday, March 21, 2013 3:18PM - 3:30PM |
W15.00005: Spin $1/2$ Heisenberg antiferromanget on kagome: Z$_2$ spin liquid with fermionic spinons Zhihao Hao, Oleg Tchernyshyov Motivated by recent numerical and experimental studies of spin $1/2$ Heisenberg antiferromagnet on kagome, we formulate a many-body model for the fermionic spinons introduced in Phys. Rev. Lett. 103, 187203. The spinons experience strong onsite attraction. They also couple with a compact U$(1)$ gauge field. The ground state of the model is generically a Z$_2$ liquid. We calculate the edge of the two-spinon continuum, which can be measured in numerics and inelastic neutron scattering experiments. [Preview Abstract] |
Thursday, March 21, 2013 3:30PM - 3:42PM |
W15.00006: Symmetry-broken phases proximate to Z2 spin liquid on Kagome lattice Gil Young Cho, Yuan-Ming Lu, Ashvin Vishwanath Recently, $Z_{2}$ spin liquid was proposed as the ground state of the Kagome quantum antiferromagnet [S. Yan, D.A. Huse, and S.R. White, {\it Science}, 332, 1173 (2011)]. We study proximate symmetry-broken phases that may appear on exiting the spin liquid phase, by tuning parameters such as further neighbor couplings. Given that the Dirac spin liquid is also a relatively low energy state, we consider models of $Z_{2}$ spin liquids that are proximate to it. Specifically we consider the s-wave paired state of an algebraic spin liquid on Kagome lattice, $Z_{2} [0,\pi]\beta$ state of Y.-M Lu, Y. Ran, and P.A. Lee, {\it Phys. Rev.} B 83, 224413 (2011)] and examine its relations with other competing states. This allows us to characterize the proximate magnetically ordered and VBS phases and criticality between them and the quantum spin liquid. [Preview Abstract] |
Thursday, March 21, 2013 3:42PM - 4:18PM |
W15.00007: A Phenomenological Theory for the $Z_2$ Spin-Liquid Phase of the $S=1/2$ Kagome Heisenberg Antiferromagnet Invited Speaker: Yuan Wan The spin-1/2 kagome Heisenberg antiferromagnet is one of the most promising candidate systems for a quantum spin liquid. However, the precise nature of its ground state is still being debated. Recent density-matrix renormalization group (DMRG) calculations show evidence for a possible $Z_2$ spin-liquid phase, the effective description of which is a $Z_2$ gauge theory [1,2]. In this work, we construct a minimal $Z_2$ gauge Hamiltonian encapsulating the DMRG phenomenology in the $S=0$ sector. We generalize Misguich's Hamiltonian [3] by including dynamical visons [4]. We show that our minimal model naturally produces the diamond resonance pattern observed in DMRG. Moreover, puzzling even-odd effects in kagome cylinders are easily explained by our model. We also predict the existence of edge spinons in certain cylindrical geometries.\\[4pt] [1] S. Yan, D. A. Huse, and S. R. White, Science \textbf{332}, 1173 (2011).\\[0pt] [2] S. Depenbrock, I. P. McCulloch, and U. Schollw\"ock, Phys. Rev. Lett. \textbf{109}, 067201 (2012).\\[0pt] [3] G. Misguich, D. Serban, and V. Pasquier, Phys. Rev. Lett. \textbf{89}, 137202 (2002).\\[0pt] [4] Y. Huh, M. Punk, and S. Sachdev, Phys. Rev. B \textbf{84}, 094419 (2011). [Preview Abstract] |
Thursday, March 21, 2013 4:18PM - 4:30PM |
W15.00008: Spinon-vison interactions in kagome-lattice spin liquids Debanjan Chowdhury, Sarang Gopalakrishnan, Subir Sachdev Recent neutron-scattering measurements on the kagome-lattice antiferromagnet Herbertsmithite [1] suggest that the ground state is well-described by a spin liquid consisting of weakly correlated (i.e., non-dispersing) singlets. We consider how these observations can be accounted for within a Schwinger-boson mean-field theory, by including interactions between spinons (i.e., the spin-1/2 excitations of the Z$_2$ spin liquid) and the topological excitations known as visons. We compute the dynamic structure factor (which is measured in the experiments of Ref. [1]) as a function of a phenomenological spinon-vison coupling constant, and discuss how this coupling constant may be extracted from numerics. [1] T.H. Han et al., to appear. [Preview Abstract] |
Thursday, March 21, 2013 4:30PM - 4:42PM |
W15.00009: Dipolar order by disorder in the classical Heisenberg antiferromagnet on the kagome lattice Gia-Wei Chern, Roderich Moessner Ever since the experiments which founded the field of highly frustrated magnetism, the kagome Heisenberg antiferromagnet has been the archetypical setting for the study of fluctuation induced exotic ordering. To this day the nature of its classical low-temperature state has remained a mystery: the non-linear nature of the fluctuations around the exponentially numerous harmonically degenerate ground states has not permitted a controlled theory, while its complex energy landscape has precluded numerical simulations at low temperature. Here we present an efficient Monte Carlo algorithm which removes the latter obstacle. Our simulations detect a low-temperature regime in which correlations saturate at a remarkably small value. Feeding these results into an effective model and analyzing the results in the framework of an appropriate field theory implies the presence of long-range dipolar spin order with a tripled unit cell. [Preview Abstract] |
Thursday, March 21, 2013 4:42PM - 4:54PM |
W15.00010: Spin Correlations in Quantum Spin Liquids on the Kagome Lattice Tyler Dodds, Yong Baek Kim The spin-1/2 Heisenberg kagome antiferromagnet, due to its highly frustrated nature, is considered a prime candidate to realize a spin-liquid ground state that breaks no symmetry and hosts fractionalized magnetic excitations. Recent numerical results indicate a close competition for the ground state between different spin-liquid states. We study spin correlations in competing phases, suggest possible experiments to distinguish different ground states, and discuss the application of these ideas to Herbertsmithite. [Preview Abstract] |
Thursday, March 21, 2013 4:54PM - 5:06PM |
W15.00011: p6 - Chiral Resonating Valence Bonds in the Kagome Antiferromagnet Assa Auerbach, Sylvain Capponi, V. Ravi Chandra, Marvin Weinstein The Kagome Heisenberg antiferromagnet is mapped onto an effective Hamiltonian on the star superlattice by Contractor Renormalization. Comparison of ground state energies on large lattices to Density Matrix Renormalization Group justifies truncation of effective interactions at range 3. Within our accuracy, magnetic and translational symmetries are not broken (i.e. a spin liquid ground state). However, we discover doublet spectral degeneracies which signal the onset of p6 - chirality symmetry breaking. This is understood by simple mean field analysis. Experimentally, the p6 chiral order parameter should split the optical phonons degeneracy near the zone center. Addition of weak next to nearest neighbor coupling is discussed. [Preview Abstract] |
Thursday, March 21, 2013 5:06PM - 5:18PM |
W15.00012: Normal Modes of Frustrated Spins on a Kagome Lattice Ashwathi Iyer, Vadim Oganesyan, Michael Lawler We study the normal modes of spins in a classical kagome antiferromagnetic Heisenberg model (KAHM), seeking evidence for the canonical and gauge-like zero modes predicted by the constrained spin model of Ref. [1]. We do so by splitting the degeneracy of the low energy configuration space through the introduction of Dzyaloshinski-Moriya (DM) interactions of strength D, performing a Monte-Carlo calculation to find the new ground state configuration, expanding the Hamiltonian to quadratic order about the minimum and diagonalizing the resulting problem to obtain the normal modes. We find that the resulting spectrum splits up into modes that scale with J, the strength of the Heisenberg interactions, and modes that scale with D and D$^{2}$/J. The latter two types of modes map directly into the canonical and gauge-like modes of the constrained spin model. In addition, we find clear evidence for ``edge modes,'' which involve the motion of the dangling triangles, in agreement with the conjecture of Ref. [1]. Our calculations shed much light on how the low energy spin dynamics of the classical KAHM behaves like a gauge theory. \\[4pt] [1] Michael J Lawler, Emergent Gauge Dynamics of Highly Frustrated Magnets, arXiv:1104.0721 [Preview Abstract] |
Thursday, March 21, 2013 5:18PM - 5:30PM |
W15.00013: Monte Carlo Simulations of FCC Kagome Lattice: Competition Between Triangular Frustration and Cubic Anisotropy Martin Leblanc, Martin Plumer, John Whitehead The impact of an effective local cubic anisotropy [1] on the magnetic states of the Heisenberg model on the FCC kagome lattice are examined through classical Metropolis Monte Carlo simulations. Previous simulations revealed that the macroscopic degeneracy of the 2D kagome exchange-coupled co-planar spin system persists in the 3D case of ABC stacked layers [2] giving rise to a discontinuous (possibly order-by-disorder) phase transition. Local cubic anisotropy is shown to reduce this degeneracy by re-orienting the spins out of the co-planar configuration. In addition, the re-oriented states are shown to carry a uniform magnetic moment. The effect of anisotropy on the order of the phase transition will also be reported. These results are relevant to Ir-Mn alloys which have been widely used by the magnetic storage industry in thin-film form as the antiferromagnetic pinning layer in GMR and TMR spin valves [2]. \\ $[1]$ L. Szunyogh, B. Lazarovits, L. Udvardi, J. Jackson, and U. Nowak, Phys. Rev. B 79, 020403(R) (2009).\\ $[2]$ V. Hemmati, M.L. Plumer, J.P. Whitehead, and B.W. Southern, Phys. Rev. B 86, 104419 (2012). [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700