Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session M28: Focus Session: Spin Liquids II |
Hide Abstracts |
Sponsoring Units: GMAG DMP Chair: Shigeki Onoda, RIKEN Room: 205 |
Wednesday, March 4, 2015 11:15AM - 11:27AM |
M28.00001: Numerical evidence of quantum melting of spin ice: quantum-classical crossover Yasuyuki Kato, Shigeki Onoda Unbiased quantum Monte-Carlo simulations are performed on the simplest case of the quantum spin ice model, namely, the nearest-neighbor spin-$\frac{1}{2}$ XXZ model on the pyrochlore lattice with an antiferromagnetic longitudinal and a weak ferromagnetic transverse exchange couplings, $J$ and $J_\perp$. On cooling across $T_{\mathrm{CSI}}\sim0.2J$, the specific heat shows a broad peak associated with a crossover to a classical Coulomb liquid regime characterized by a remnant of the pinch-point singularity in longitudinal spin correlations as well as the Pauling ice entropy for $|J_\perp|\ll J$, as in classical spin ice. On further cooling, the entropy restarts gradually decaying to zero for $J_\perp>J_{\perp c}\sim-0.104J$, as expected for bosonic quantum Coulomb liquids. With negatively increasing $J_\perp$ across $J_{\perp c}$, a first-order transition occurs at a nonzero temperature from the quantum Coulomb liquid to an XY ferromagnet. Relevance to magnetic rare-earth pyrochlore oxides is discussed. [Preview Abstract] |
Wednesday, March 4, 2015 11:27AM - 11:39AM |
M28.00002: Possible algebraic spin liquid in half-filled Hubbard model at intermediate U/t Zixiang Li, Zi Yang Meng, Hong Yao Using large-scale fermion-sign-free projective Determinant Quantum Monte-Carlo (DQMC) method, we study the half-filled Hubbard model on the square lattice with staggered-flux. We calculate the single-particle gap, charge gap, as well as the improved dimensionless estimator of the antiferromagnetic (AF) order parameter, and map out the ground state phase diagram of this model spanned by U/t and staggered-flux. The lattice in our DQMC simulations has 2*L*L sites with largest L$=$28. In the case of $\backslash $pi-flux, finite-size scaling analysis indicates a possible algebraic quantum spin liquid phase between the semi-metal phase at small U/t and the AF phase at large U/t. The algebraic spin liquid occurs in the arrange of 5.4 \textless U/t \textless 5.6. When the staggered-flux is smaller than the critical value of about $\backslash $pi/10, the Fermi velocity in this system is largely anisotropic and it exhibits a direct transition from semi-metal phase to AF phase. [Preview Abstract] |
Wednesday, March 4, 2015 11:39AM - 11:51AM |
M28.00003: Confinement-deconfinement transition in the algebraic RVB states Ji-Quan Pei, Shao-Kai Jian, Hong Yao Deconfined algebraic spin liquids are usually expected when Gutzwiller projecting the non-interacting wave function of half-filled electrons on the square lattice with staggered flux $\phi$. However, our large-scale variational Monte Carlo simulations show that there is the confinement-deconfinement transition at $\phi=\phi_c$ where $\phi_c \sim 0.2$ is the critical flux. When $0<\phi<\phi_c$, spinors are confined and the ground state develops an unexpected antiferromagnetic Neel ordering. From renormalization group analysis of anisotropic Dirac fermions coupled with U(1) compact gauge fields, we argue that the confinement of spinors in the Gutzwiller projected wave function might be due to the large anisotropy of Fermi velocity of Dirac fermions. [Preview Abstract] |
Wednesday, March 4, 2015 11:51AM - 12:03PM |
M28.00004: ABSTRACT WITHDRAWN |
Wednesday, March 4, 2015 12:03PM - 12:15PM |
M28.00005: Schwinger boson spin liquid states on square lattice: projective symmetry group study Xu Yang, Fa Wang We will report our results on possible spin liquids on square lattice that respect all lattice symmetries and time-reversal symmetry within the framework of Schwinger boson (mean-field) theory. Such spin liquids have spin gap and emergent $Z_2$ gauge field excitations. We classify them by the projective symmetry group method, and find six spin liquid states that are potentially relevant to the $J_1$-$J_2$ Heisenberg model. The properties of these states are studied under mean-field approximation and by projected wave functions on small lattices. Interestingly we find a spin liquid statethat can go through continuous phase transitions to either N\'eel magnetic order or magnetic order of wavevector at Brillouin zone edge center. We propose that this state may be realized in $J_1$-$J_2$ Heisenberg model with ring exchange. [Preview Abstract] |
Wednesday, March 4, 2015 12:15PM - 12:51PM |
M28.00006: Projective symmetry of partons in Kitaev's honeycomb model Invited Speaker: Paula Mellado Low-energy states of quantum spin liquids are thought to involve partons living in a gauge-field background. We study the spectrum of Majorana fermions of Kitaev's honeycomb model on spherical clusters. The gauge field endows the partons with half-integer orbital angular momenta. As a consequence, the multiplicities reflect not the point-group symmetries of the cluster, but rather its projective symmetries, operations combining physical and gauge transformations. The projective symmetry group of the ground state is the double cover of the point group. [Preview Abstract] |
Wednesday, March 4, 2015 12:51PM - 1:03PM |
M28.00007: Chiral spin liquid and emergent anyons in a Kagome lattice Mott insulator Bela Bauer, Lukasz Cincio, Brendan P. Keller, Michele Dolfi, Guifre Vidal, Simon Trebst, Andreas W. W. Ludwig One of the earliest proposals for a topological phase in a quantum spin system was the chiral spin liquid put forward by Kalmeyer and Laughlin in 1987 as the bosonic analogue of the fractional quantum Hall effect. Here, we examine a physically motivated model for a Mott insulator on the Kagome lattice with broken time-reversal (TR) symmetry that gives rise to a chiral spin liquid. We present unambiguous numerical identification and characterization of the universal topological properties of the phase, including ground state degeneracy, edge physics, and anyonic bulk excitations. To this end, we use a variety of powerful numerical probes, including the entanglement spectrum and modular transformations. We then discuss the phase diagram resulting from the competition of the TR symmetry breaking chiral term and a TR-symmetric Heisenberg term, which on the Kagome lattice has been argued to give rise to a TR-symmetric topological phase. In particular, we elucidate the dynamics of the chiral phase upon approaching the putative topological phase transition. [Preview Abstract] |
Wednesday, March 4, 2015 1:03PM - 1:15PM |
M28.00008: Impact of non-Abelian anyons on criticality Marc Schulz, Fiona Burnell Topological order provides an interesting playground to investigate criticality in phase transitions with no local order parameter where the condensing excitations interact statistically. We investigate the impact of these exchange statistics on critical properties by comparing two closely related models, which differ only by the presence or absence of such long-ranged statistical interactions for the condensed excitations: \begin{enumerate} \item The Ising string-net Hamiltonian, in which the transition is between a topologically ordered phase (with doubled Ising topological order) and a trivial phase. The excitations that condense across this transition are achiral non-Abelian anyons. \item The Ashkin-Teller model on a triangular lattice, in which the transition is from a paramagnetic to a ferromagnetic phase. \end{enumerate} We show that the non-Abelian excitations in the first model can be mapped onto the spin degrees of freedom of the second, and that the mapping captures all relevant features except the non-Abelian statistics. We derive the low-energy spectra of these models by means of high-order perturbation theory and exact diagonalization to study the resulting differences in their critical behavior. [Preview Abstract] |
Wednesday, March 4, 2015 1:15PM - 1:27PM |
M28.00009: Variational Monte Carlo Study of a Non-Abelian Spin-1 Spin Liquid Julia Wildeboer, N.E. Bonesteel Using variational Monte Carlo we analyze the properties of a non-Abelian spin-1 spin liquid state proposed in [1]. In this state the bosonic $\nu=1$ Moore-Read Pfaffian wavefunction is interpreted as a wavefunction for a gas of bosons on a 2D square lattice with one flux quantum per plaquette. For this wavefunction the number of bosons on a given lattice site can be 0,1 or 2, corresponding, respectively, to $S_z = -1,0$ or 1 for a spin-1 degree of freedom on that site. Calculations are performed both in the planar geometry and on the torus. For the torus there are three distinct states corresponding to the three-fold degeneracy of the $\nu=1$ bosonic Moore-Read state, and we show that the correlation functions in these states become identical in the limit of large system size. The Renyi entanglement entropy is also calculated for different system partitions in order to extract the topological entropy $\gamma = \ln {\cal D}$ where ${\cal D}$ is the total quantum dimension, predicted to be ${\cal D} = 2$ for this state. \newline [1] M. Greiter and R. Thomale, Phys. Rev. Lett. 102, 207203 (2009). [Preview Abstract] |
Wednesday, March 4, 2015 1:27PM - 1:39PM |
M28.00010: Coherent Transmutation of Electrons into Fractionalized Anyons Maissam Barkeshli, Erez Berg, Steven Kivelson Electrons have three quantized properties -- charge, spin, and Fermi statistics -- that are directly responsible for a vast array of phenomena. Here we show how these properties can be coherently and dynamically stripped from the electron as it enters certain exotic states of matter known as a quantum spin liquid (QSL). In a QSL, electron spins collectively form a highly entangled quantum state that gives rise to emergent gauge forces and fractionalization of spin, charge, and statistics. We show that certain QSLs host distinct, topologically robust boundary types, some of which allow the electron to coherently enter the QSL as a fractionalized quasiparticle, leaving its spin, charge, or statistics behind. We use these ideas to propose a number of universal, conclusive experimental signatures that would establish fractionalization in QSLs. [Preview Abstract] |
Wednesday, March 4, 2015 1:39PM - 2:15PM |
M28.00011: Chiral spin liquid in the frustrated XY model on the honeycomb lattice Invited Speaker: Tigran Sedrakyan A honeycomb lattice allowing hops between nearest- and next-nearest neighbors hosts ``moat'' bands with degenerate energy minima attained along closed lines in Brillouin zone. If populated with hard-core bosons, a variety of unconventional ground states stabilizes. We argue that the degeneracy prevents Bose condensation, stabilizing novel spin liquid phases including composite fermion state and a chiral spin liquid. The latter stabilizes at half-filling, when the system is equivalent to $s = 1/2$ XY model at zero magnetic field. Absence of condensation means no spontaneous polarization in XY plane, however our consideration indicates formation of a state spontaneously breaking the time-reversal symmetry. This state has a bulk gap and chiral gapless edge excitations, and is similar to the one in Haldane's ``quantum Hall effect without Landau levels'' in its topologically nontrivial sector with Chen number $C=\pm 1$. The applications of the developed analytical theory include an explanation of recent unexpected numerical findings and a suggestion of a chiral spin liquid realization in experiments with cold atoms in optical lattices. [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