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Xiang J, Zhang C, Gao Y, Schmidt W, Schmalzl K, Wang CW, Li B, Xi N, Liu XY, Jin H, Li G, Shen J, Chen Z, Qi Y, Wan Y, Jin W, Li W, Sun P, Su G. Giant magnetocaloric effect in spin supersolid candidate Na 2BaCo(PO 4) 2. Nature 2024; 625:270-275. [PMID: 38200301 DOI: 10.1038/s41586-023-06885-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 11/21/2023] [Indexed: 01/12/2024]
Abstract
Supersolid, an exotic quantum state of matter that consists of particles forming an incompressible solid structure while simultaneously showing superfluidity of zero viscosity1, is one of the long-standing pursuits in fundamental research2,3. Although the initial report of 4He supersolid turned out to be an artefact4, this intriguing quantum matter has inspired enthusiastic investigations into ultracold quantum gases5-8. Nevertheless, the realization of supersolidity in condensed matter remains elusive. Here we find evidence for a quantum magnetic analogue of supersolid-the spin supersolid-in the recently synthesized triangular-lattice antiferromagnet Na2BaCo(PO4)2 (ref. 9). Notably, a giant magnetocaloric effect related to the spin supersolidity is observed in the demagnetization cooling process, manifesting itself as two prominent valley-like regimes, with the lowest temperature attaining below 100 mK. Not only is there an experimentally determined series of critical fields but the demagnetization cooling profile also shows excellent agreement with the theoretical simulations with an easy-axis Heisenberg model. Neutron diffractions also successfully locate the proposed spin supersolid phases by revealing the coexistence of three-sublattice spin solid order and interlayer incommensurability indicative of the spin superfluidity. Thus, our results reveal a strong entropic effect of the spin supersolid phase in a frustrated quantum magnet and open up a viable and promising avenue for applications in sub-kelvin refrigeration, especially in the context of persistent concerns about helium shortages10,11.
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Affiliation(s)
- Junsen Xiang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Chuandi Zhang
- School of Physics, Beihang University, Beijing, China
| | - Yuan Gao
- School of Physics, Beihang University, Beijing, China
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, China
| | - Wolfgang Schmidt
- Jülich Centre for Neutron Science at Institut Laue-Langevin (ILL), Forschungszentrum Jülich GmbH, Grenoble Cedex 9, France
| | - Karin Schmalzl
- Jülich Centre for Neutron Science at Institut Laue-Langevin (ILL), Forschungszentrum Jülich GmbH, Grenoble Cedex 9, France
| | - Chin-Wei Wang
- Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales, Australia
| | - Bo Li
- School of Physics, Beihang University, Beijing, China
| | - Ning Xi
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, China
| | - Xin-Yang Liu
- School of Physics, Beihang University, Beijing, China
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, China
| | - Hai Jin
- Department of Astronomy, Tsinghua University, Beijing, China
| | - Gang Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Jun Shen
- Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Ziyu Chen
- School of Physics, Beihang University, Beijing, China
| | - Yang Qi
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China
| | - Yuan Wan
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Wentao Jin
- School of Physics, Beihang University, Beijing, China.
| | - Wei Li
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, China.
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijng, China.
- Peng Huanwu Collaborative Center for Research and Education, Beihang University, Beijing, China.
| | - Peijie Sun
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.
| | - Gang Su
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijng, China.
- Kavli Institute for Theoretical Sciences, and School of Physical Sciences, University of Chinese Academy of Sciences, Beijng, China.
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Abstract
We study the ground state phase diagram of a two dimensional mixed-spin system of coupled alternating spin-1 and 1/2 chains with a stripe supersolid phase. Utilizing different analytical and numerical approaches such as mean field approximation, cluster mean field theory and linear spin wave theory, we demonstrate that our system displays a rich ground state phase diagram including novel stripe supersolid, solids with different fillings and super-counterfluid phases, in addition to a stripe solid with half filling, superfluid and Mott insulating phases. In order to find a minimal mixed-spin model for stripe supersolidity, in the second part of the paper we consider two kinds of mixed-spin system of coupled alternating spin-1 and 1/2 chains with (i) anisotropic nearest neighbor interactions, (ii) anisotropic hoppings and study their ground state phase diagrams. We demonstrate that, for the systems with uniform hoppings, the repulsive intra-chains interactions are necessary for stripe supersolidity. In this case the minimal two dimensional mixed-spin model is a system of spin-1 and spin-1/2 XXZ chains, interacting via Ising Hamiltonian. In the case of anisotropic hoppings, a system of coupled Ising chains is the minimal model.
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3
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Alet F, Damle K, Pujari S. Sign-Problem-Free Monte Carlo Simulation of Certain Frustrated Quantum Magnets. PHYSICAL REVIEW LETTERS 2016; 117:197203. [PMID: 27858437 DOI: 10.1103/physrevlett.117.197203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Indexed: 06/06/2023]
Abstract
We introduce a quantum Monte Carlo (QMC) method for efficient sign-problem-free simulations of a broad class of frustrated S=1/2 antiferromagnets using the basis of spin eigenstates of clusters to avoid the severe sign problem faced by other QMC methods. We demonstrate the utility of the method in several cases with competing exchange interactions and flag important limitations as well as possible extensions of the method.
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Affiliation(s)
- Fabien Alet
- Laboratoire de Physique Théorique, IRSAMC, Université de Toulouse, CNRS, 31062 Toulouse, France
| | - Kedar Damle
- Department of Theoretical Physics, Tata Institute of Fundamental Research, Mumbai 400 005, India
| | - Sumiran Pujari
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055, USA
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Zhang XF, Hu S, Pelster A, Eggert S. Quantum Domain Walls Induce Incommensurate Supersolid Phase on the Anisotropic Triangular Lattice. PHYSICAL REVIEW LETTERS 2016; 117:193201. [PMID: 27858459 DOI: 10.1103/physrevlett.117.193201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Indexed: 06/06/2023]
Abstract
We investigate the extended hard-core Bose-Hubbard model on the triangular lattice as a function of spatial anisotropy with respect to both hopping and nearest-neighbor interaction strength. At half-filling the system can be tuned from decoupled one-dimensional chains to a two-dimensional solid phase with alternating density order by adjusting the anisotropic coupling. At intermediate anisotropy, however, frustration effects dominate and an incommensurate supersolid phase emerges, which is characterized by incommensurate density order as well as an anisotropic superfluid density. We demonstrate that this intermediate phase results from the proliferation of topological defects in the form of quantum bosonic domain walls. Accordingly, the structure factor has peaks at wave vectors, which are linearly related to the number of domain walls in a finite system in agreement with extensive quantum Monte Carlo simulations. We discuss possible connections with the supersolid behavior in the high-temperature superconducting striped phase.
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Affiliation(s)
- Xue-Feng Zhang
- Physics Department and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
- Max-Planck-Institute for the Physics of Complex Systems, 01187 Dresden, Germany
- State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Shijie Hu
- Physics Department and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Axel Pelster
- Physics Department and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Sebastian Eggert
- Physics Department and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
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5
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Damle K. Melting of Three-Sublattice Order in Easy-Axis Antiferromagnets on Triangular and Kagome Lattices. PHYSICAL REVIEW LETTERS 2015; 115:127204. [PMID: 26431015 DOI: 10.1103/physrevlett.115.127204] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2014] [Indexed: 06/05/2023]
Abstract
When the constituent spins have an energetic preference to lie along an easy axis, triangular and kagome lattice antiferromagnets often develop long-range order that distinguishes the three sublattices of the underlying triangular Bravais lattice. In zero magnetic field, this three-sublattice order melts either in a two-step manner, i.e., via an intermediate phase with power-law three-sublattice order controlled by a temperature-dependent exponent η(T)∈(1/9,1/4), or via a transition in the three-state Potts universality class. Here, I predict that the uniform susceptibility to a small easy-axis field B diverges as χ(B)∼|B|^{-[(4-18η)/(4-9η)]} in a large part of the intermediate power-law ordered phase [corresponding to η(T)∈(1/9,2/9)], providing an easy-to-measure thermodynamic signature of two-step melting. I also show that these two melting scenarios can be generically connected via an intervening multicritical point and obtain numerical estimates of multicritical exponents.
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Affiliation(s)
- Kedar Damle
- Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400005, India
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6
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Tocchio LF, Gros C, Zhang XF, Eggert S. Phase diagram of the triangular extended Hubbard model. PHYSICAL REVIEW LETTERS 2014; 113:246405. [PMID: 25541786 DOI: 10.1103/physrevlett.113.246405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Indexed: 06/04/2023]
Abstract
We study the extended Hubbard model on the triangular lattice as a function of filling and interaction strength. The complex interplay of kinetic frustration and strong interactions on the triangular lattice leads to exotic phases where long-range charge order, antiferromagnetic order, and metallic conductivity can coexist. Variational Monte Carlo simulations show that three kinds of ordered metallic states are stable as a function of nearest neighbor interaction and filling. The coexistence of conductivity and order is explained by a separation into two functional classes of particles: part of them contributes to the stable order, while the other part forms a partially filled band on the remaining substructure. The relation to charge ordering in charge transfer salts is discussed.
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Affiliation(s)
- Luca F Tocchio
- Institute for Theoretical Physics, University of Frankfurt, Max-von-Laue-Straße 1, D-60438 Frankfurt, Germany and CNR-IOM-Democritos National Simulation Centre and International School for Advanced Studies (SISSA), Via Bonomea 265, I-34136 Trieste, Italy
| | - Claudius Gros
- Institute for Theoretical Physics, University of Frankfurt, Max-von-Laue-Straße 1, D-60438 Frankfurt, Germany
| | - Xue-Feng Zhang
- Physics Department and Research Center OPTIMAS, University of Kaiserslautern, D-67663 Kaiserslautern, Germany
| | - Sebastian Eggert
- Physics Department and Research Center OPTIMAS, University of Kaiserslautern, D-67663 Kaiserslautern, Germany
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7
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Kourtis S, Daghofer M. Combined topological and Landau order from strong correlations in Chern bands. PHYSICAL REVIEW LETTERS 2014; 113:216404. [PMID: 25479510 DOI: 10.1103/physrevlett.113.216404] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Indexed: 06/04/2023]
Abstract
We present a class of states with both topological and conventional Landau order that arise out of strongly interacting spinless fermions in fractionally filled and topologically nontrivial bands with Chern number C=±1. These quantum states show the features of fractional Chern insulators, such as fractional Hall conductivity and interchange of ground-state levels upon insertion of a magnetic flux. In addition, they exhibit charge order and a related additional trivial ground-state degeneracy. Band mixing and geometric frustration of the charge pattern place these lattice states markedly beyond a single-band description.
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Affiliation(s)
- Stefanos Kourtis
- Institute for Theoretical Solid State Physics, IFW Dresden, 01171 Dresden, Germany
| | - Maria Daghofer
- Institute for Theoretical Solid State Physics, IFW Dresden, 01171 Dresden, Germany
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8
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Yamamoto D, Marmorini G, Danshita I. Quantum phase diagram of the triangular-lattice XXZ model in a magnetic field. PHYSICAL REVIEW LETTERS 2014; 112:127203. [PMID: 24724677 DOI: 10.1103/physrevlett.112.127203] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Indexed: 06/03/2023]
Abstract
The triangular lattice of S=1/2 spins with XXZ anisotropy is a ubiquitous model for various frustrated systems in different contexts. We determine the quantum phase diagram of the model in the plane of the anisotropy parameter and the magnetic field by means of a large-size cluster mean-field method with a scaling scheme. We find that quantum fluctuations break up the nontrivial continuous degeneracy into two first-order phase transitions. In between the two transition boundaries, the degeneracy-lifting results in the emergence of a new coplanar phase not predicted in the classical counterpart of the model. We suggest that the quantum phase transition to the nonclassical coplanar state can be observed in triangular-lattice antiferromagnets with large easy-plane anisotropy or in the corresponding optical-lattice systems.
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Affiliation(s)
- Daisuke Yamamoto
- Condensed Matter Theory Laboratory, RIKEN, Saitama 351-0198, Japan
| | - Giacomo Marmorini
- Condensed Matter Theory Laboratory, RIKEN, Saitama 351-0198, Japan and Research and Education Center for Natural Sciences, Keio University, Kanagawa 223-8521, Japan
| | - Ippei Danshita
- Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan and Computational Condensed Matter Physics Laboratory, RIKEN, Saitama 351-0198, Japan
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9
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Windpassinger P, Sengstock K. Engineering novel optical lattices. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2013; 76:086401. [PMID: 23828639 DOI: 10.1088/0034-4885/76/8/086401] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Optical lattices have developed into a widely used and highly recognized tool to study many-body quantum physics with special relevance for solid state type systems. One of the most prominent reasons for this success is the high degree of tunability in the experimental setups. While at the beginning quasi-static, cubic geometries were mainly explored, the focus of the field has now shifted toward new lattice topologies and the dynamical control of lattice structures. In this review we intend to give an overview of the progress recently achieved in this field on the experimental side. In addition, we discuss theoretical proposals exploiting specifically these novel lattice geometries.
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Affiliation(s)
- Patrick Windpassinger
- Institut für Laserphysik and Zentrum für Optische Quantentechnologien, Universität Hamburg, Hamburg, Germany.
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10
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Wierschem K, Sengupta P. Columnar antiferromagnetic order and spin supersolid phase on the extended Shastry-Sutherland lattice. PHYSICAL REVIEW LETTERS 2013; 110:207207. [PMID: 25167448 DOI: 10.1103/physrevlett.110.207207] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Indexed: 06/03/2023]
Abstract
We use large scale quantum Monte Carlo simulations to study an extended version of the canonical Shastry-Sutherland model--including additional interactions and exchange anisotropy--over a wide range of interaction parameters and an applied magnetic field. The model is appropriate for describing the low energy properties of some members of the rare earth tetraborides. Working in the limit of large Ising-like exchange anisotropy, we demonstrate the stabilization of columnar antiferromagnetic order in the ground state at zero field and an extended magnetization plateau at 1/2 the saturation magnetization in the presence of an applied longitudinal magnetic field--qualitatively similar to experimentally observed low-temperature phases in ErB(4). Our results show that for an optimal range of exchange parameters, a spin supersolid ground state is realized over a finite range of an applied field between the columnar antiferromagnetic phase and the magnetization plateau. The full momentum dependence of the longitudinal and transverse components of the static structure factor is calculated in the spin supersolid phase to demonstrate the simultaneous existence of diagonal and off-diagonal long-range order. Our results provide crucial guidance in designing further experiments to search for the interesting spin supersolid phase in ErB(4).
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Affiliation(s)
- Keola Wierschem
- School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Pinaki Sengupta
- School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
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11
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Fellows JM, Carr ST, Hooley CA, Schmalian J. Unbinding of giant vortices in states of competing order. PHYSICAL REVIEW LETTERS 2012; 109:155703. [PMID: 23102335 DOI: 10.1103/physrevlett.109.155703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Indexed: 06/01/2023]
Abstract
We consider a two-dimensional system with two order parameters, one with O(2) symmetry and one with O(M), near a point in parameter space where they couple to become a single O(2+M) order. While the O(2) sector supports vortex excitations, these vortices must somehow disappear as the high symmetry point is approached. We develop a variational argument which shows that the size of the vortex cores diverges as 1/√Δ and the Berezinskii-Kosterlitz-Thouless transition temperature of the O(2) order vanishes as 1/ln(1/Δ), where Δ denotes the distance from the high-symmetry point. Our physical picture is confirmed by a renormalization group analysis which gives further logarithmic corrections, and demonstrates full symmetry restoration within the cores.
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Affiliation(s)
- J M Fellows
- School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom
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12
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Baranov MA, Dalmonte M, Pupillo G, Zoller P. Condensed Matter Theory of Dipolar Quantum Gases. Chem Rev 2012; 112:5012-61. [DOI: 10.1021/cr2003568] [Citation(s) in RCA: 480] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- M. A. Baranov
- Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck, Austria
- Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Austria
- RRC “Kurchatov Institute”,
Kurchatov Square 1, 123182, Moscow, Russia
| | - M. Dalmonte
- Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck, Austria
- Dipartimento di Fisica dell’Università
di Bologna, via Irnerio 46, 40126 Bologna, Italy
| | - G. Pupillo
- Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck, Austria
- Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Austria
- ISIS (UMR 7006) and IPCMS (UMR
7504), Université de Strasbourg and CNRS, Strasbourg, France
| | - P. Zoller
- Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck, Austria
- Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Austria
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13
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Block MS, Mishmash RV, Kaul RK, Sheng DN, Motrunich OI, Fisher MPA. Exotic gapless mott insulators of bosons on multileg ladders. PHYSICAL REVIEW LETTERS 2011; 106:046402. [PMID: 21405343 DOI: 10.1103/physrevlett.106.046402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2010] [Indexed: 05/30/2023]
Abstract
We present evidence for an exotic gapless insulating phase of hard-core bosons on multileg ladders with a density commensurate with the number of legs. In particular, we study in detail a model of bosons moving with direct hopping and frustrating ring exchange on a 3-leg ladder at ν=1/3 filling. For sufficiently large ring exchange, the system is insulating along the ladder but has two gapless modes and power law transverse density correlations at incommensurate wave vectors. We propose a determinantal wave function for this phase and find excellent comparison between variational Monte Carlo and density matrix renormalization group calculations on the model Hamiltonian, thus providing strong evidence for the existence of this exotic phase. Finally, we discuss extensions of our results to other N-leg systems and to N-layer two-dimensional structures.
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Affiliation(s)
- Matthew S Block
- Department of Physics, University of California, Santa Barbara, California 93106, USA
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14
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15
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Seabra L, Shannon N. Supersolid phases in a realistic three-dimensional spin model. PHYSICAL REVIEW LETTERS 2010; 104:237205. [PMID: 20867267 DOI: 10.1103/physrevlett.104.237205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 05/07/2010] [Indexed: 05/29/2023]
Abstract
Supersolid phases, in which a superfluid component coexists with conventional crystalline long range order, have recently attracted a great deal of attention in the context of both solid helium and quantum spin systems. Motivated by recent experiments on 2H-AgNiO2, we study the magnetic phase diagram of a realistic three-dimensional spin model with single-ion anisotropy and competing interactions on a layered triangular lattice, using classical Monte Carlo simulation techniques, complemented by spin-wave calculations. For parameters relevant to experiment, we find a cascade of different phases as a function of magnetic field, including three phases which are supersolids in the sense of Liu and Fisher. One of these phases is continuously connected with the collinear ground state of AgNiO2, and is accessible at relatively low values of magnetic field. The nature of this transition, and its possible observation, are discussed.
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Affiliation(s)
- Luis Seabra
- H. H. Wills Physics Laboratory, University of Bristol, Tyndall Av, BS8-1TL, United Kingdom
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16
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Ng KK, Chen YC, Tzeng YC. Quarter-filled supersolid and solid phases in the extended Bose-Hubbard model. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:185601. [PMID: 21393687 DOI: 10.1088/0953-8984/22/18/185601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We numerically study the ground state phase diagram of the two-dimensional hard-core Bose-Hubbard model with nearest-(V(1)) and next-nearest-neighbour (V(2)) repulsions. In particular, we focus on the quarter-filled phases where one supersolid and two solid phases are observed. Using both canonical and grand canonical quantum Monte Carlo (QMC) methods and a mean-field calculation, we provide evidence for the existence of a commensurate supersolid. Despite the two possible diagonal long-range orderings for the solid phase, only one kind of supersolid phase is found to be energetically stable. The competition between the two solid phases manifests itself as a first-order phase transition around 2V(2) ∼ V(1). The change of order parameters as a function of the chemical potential is also presented.
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Affiliation(s)
- Kwai-Kong Ng
- Department of Physics, Tunghai University, Taichung 40704, Taiwan
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17
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Pollet L, Picon JD, Büchler HP, Troyer M. Supersolid phase with cold polar molecules on a triangular lattice. PHYSICAL REVIEW LETTERS 2010; 104:125302. [PMID: 20366542 DOI: 10.1103/physrevlett.104.125302] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Revised: 08/11/2009] [Indexed: 05/29/2023]
Abstract
We study a system of heteronuclear molecules on a triangular lattice and analyze the potential of this system for the experimental realization of a supersolid phase. The ground state phase diagram contains superfluid, solid, and supersolid phases. At finite temperatures and strong interactions there is an additional emulsion region, in contrast with similar models with short-range interactions. We derive the maximal critical temperature T{c} and the corresponding entropy S/N=0.04(1) for supersolidity and find feasible experimental conditions for its realization.
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Affiliation(s)
- L Pollet
- Physics Department, Harvard University, Cambridge, Massachusetts 02138, USA
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18
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Capogrosso-Sansone B, Trefzger C, Lewenstein M, Zoller P, Pupillo G. Quantum phases of cold polar molecules in 2D optical lattices. PHYSICAL REVIEW LETTERS 2010; 104:125301. [PMID: 20366541 DOI: 10.1103/physrevlett.104.125301] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Revised: 02/22/2010] [Indexed: 05/29/2023]
Abstract
We study the quantum phases of hard-core bosonic polar molecules on a two-dimensional square lattice interacting via repulsive dipole-dipole interactions. In the limit of small tunneling, we find evidence for a devil's staircase, where Mott solids appear at rational fillings of the lattice. For finite tunneling, we establish the existence of extended regions of parameters where the ground state is a supersolid, obtained by doping the solids either with particles or vacancies. We discuss the effects of finite temperature and finite-size confining potentials as relevant to experiments.
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Affiliation(s)
- B Capogrosso-Sansone
- ITAMP, Harvard-Smithsonian Center of Astrophysics, Cambridge, Massachusetts 02138, USA
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19
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Ralko A, Trousselet F, Poilblanc D. Quantum melting of valence-bond crystal insulators and novel supersolid phase at commensurate density. PHYSICAL REVIEW LETTERS 2010; 104:127203. [PMID: 20366561 DOI: 10.1103/physrevlett.104.127203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2009] [Revised: 03/02/2010] [Indexed: 05/29/2023]
Abstract
Bosonic and fermionic Hubbard models on the checkerboard lattice are studied numerically for infinite on-site repulsion. At particle density n=1/4 and strong nearest-neighbor repulsion, insulating Valence-Bond crystals (VBC) of resonating particle pairs are stabilized. Their melting into superfluid or metallic phases under increasing hopping is investigated at T=0 K. We identify a novel and unconventional commensurate VBC supersolid region, precursor to the melting of the bosonic crystal. Hardcore bosons (spins) are compared to fermions (electrons), as well as positive to negative (frustrating) hoppings.
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Affiliation(s)
- Arnaud Ralko
- Institut Néel UPR2940, CNRS and Université de Grenoble, F-38000 France
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20
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Heidarian D, Paramekanti A. Supersolidity in the triangular lattice spin-1/2 XXZ model: a variational perspective. PHYSICAL REVIEW LETTERS 2010; 104:015301. [PMID: 20366369 DOI: 10.1103/physrevlett.104.015301] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Revised: 11/09/2009] [Indexed: 05/29/2023]
Abstract
We study the spin-1/2 XXZ model on the triangular lattice with a nearest neighbor antiferromagnetic Ising coupling J(z) > 0 and unfrustrated (J(perpendicular) < 0) or frustrated (J(perpendicular) >0) kinetic terms in a zero magnetic field. Incorporating long-range Jastrow correlations over a mean-field spin state, we obtain the variational phase diagram of this model on large lattices for arbitrary J(z) and either sign of J(perpendicular). For J(perpendicular) < 0, we find a square root(3) x square root(3) supersolid for J(z)/J(perpendicular)| approximately > 4.7, in excellent agreement with quantum Monte Carlo data. For J(perpendicular) > 0, a distinct square root(3) x square root(3) supersolid is found to emerge for J(z)/J(perpendicular) > or = 1. Both supersolids exhibit a spontaneous density deviation from half-filling. At J(z)/J(perpendicular) = infinity, the crystalline order parameters of these two supersolids are nearly identical, consistent with exact results.
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Affiliation(s)
- Dariush Heidarian
- Department of Physics, University of Toronto, Toronto, Ontario, Canada M5S 1A7
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21
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Raczkowski M, Poilblanc D. Supersolid phases of a doped valence-bond quantum antiferromagnet: evidence for a coexisting superconducting order parameter. PHYSICAL REVIEW LETTERS 2009; 103:027001. [PMID: 19659234 DOI: 10.1103/physrevlett.103.027001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Indexed: 05/28/2023]
Abstract
Motivated by numerical evidence of the valence-bond ground state of the two-dimensional Heisenberg pyrochlore lattice, we argue using a t-J model that it evolves under doping into novel phases characterized by superconductivity coexisting with the underlying valence-bond solid order. A fermionic mean-field theory supplemented by exact diagonalization results provide strong arguments in favor of the stability of such supersolid phases. The resemblance with modulated superconducting patterns in high-Tc cuprates as well as possible relevance to frustrated noncuprate superconductors such as spinels and pyrochlores is discussed.
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Affiliation(s)
- Marcin Raczkowski
- Marian Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, PL-30059 Kraków, Poland
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22
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Fortune NA, Hannahs ST, Yoshida Y, Sherline TE, Ono T, Tanaka H, Takano Y. Cascade of magnetic-field-induced quantum phase transitions in a spin-1/2 triangular-lattice antiferromagnet. PHYSICAL REVIEW LETTERS 2009; 102:257201. [PMID: 19659114 DOI: 10.1103/physrevlett.102.257201] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Indexed: 05/28/2023]
Abstract
We report magnetocaloric and magnetic-torque evidence that in Cs2CuBr4--a geometrically frustrated Heisenberg S=1/2 triangular-lattice antiferromagnet--quantum fluctuations stabilize a series of spin states at simple increasing fractions of the saturation magnetization Ms. Only the first of these states--at M=1/3Ms--has been theoretically predicted. We discuss how the higher fraction quantum states might arise and propose model spin arrangements. We argue that the first-order nature of the transitions into those states is due to strong lowering of the energies by quantum fluctuations, with implications for the general character of quantum phase transitions in geometrically frustrated systems.
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Affiliation(s)
- N A Fortune
- Department of Physics, Smith College, Northampton, Massachusetts 01063, USA
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23
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Andrews S, De Sterck H, Inglis S, Melko RG. Monte Carlo study of degenerate ground states and residual entropy in a frustrated honeycomb lattice Ising model. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 79:041127. [PMID: 19518193 DOI: 10.1103/physreve.79.041127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Indexed: 05/27/2023]
Abstract
We study a classical fully frustrated honeycomb lattice Ising model using Markov-chain Monte Carlo methods and exact calculations. The Hamiltonian realizes a degenerate ground-state manifold of equal-energy states, where each hexagonal plaquette of the lattice has one and only one unsatisfied bond, with an extensive residual entropy that grows as the number of spins N. Traditional single-spin-flip Monte Carlo methods fail to sample all possible spin configurations in this ground state efficiently, due to their separation by large energy barriers. We develop a nonlocal "chain-flip" algorithm that solves this problem, and demonstrate its effectiveness on the Ising Hamiltonian with and without perturbative interactions. The two perturbations considered are a slightly weakened bond and an external magnetic field h. For some cases, the chain-flip move is necessary for the simulation to find an ordered ground state. In the case of the magnetic field, two magnetized ground states with nonextensive entropy are found, and two special values of h exist where the residual entropy again becomes extensive, scaling proportionally to N ln phi, where phi is the golden ratio.
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Affiliation(s)
- Shawn Andrews
- Department of Applied Mathematics, University of Waterloo, Ontario, Canada N2L 3G1
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24
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Wang F, Pollmann F, Vishwanath A. Extended supersolid phase of frustrated hard-core bosons on a triangular lattice. PHYSICAL REVIEW LETTERS 2009; 102:017203. [PMID: 19257235 DOI: 10.1103/physrevlett.102.017203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2008] [Indexed: 05/27/2023]
Abstract
We study a model of hard-core bosons with frustrated nearest-neighbor hopping (t) and repulsion (V) on the triangular lattice. We argue for a supersolid ground state in the large repulsion (V>>|t|) limit where a dimer representation applies, by constructing a unitary mapping to the well-understood unfrustrated hopping case. This generalized "Marshall sign rule" allows us to establish the precise nature of the supersolid order by utilizing a recently proposed dimer variational wave function, whose correlations can be efficiently calculated using the Grassmann approach. By continuity, a supersolid is predicted over the wide parameter range, V>-2t>0. This also establishes a simple phase diagram for the triangular lattice spin 1/2 XXZ antiferromagnet.
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Affiliation(s)
- Fa Wang
- Department of Physics, University of California, Berkeley, California 94720, USA
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25
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Hotta C, Pollmann F. Dimensional tuning of electronic states under strong and frustrated interactions. PHYSICAL REVIEW LETTERS 2008; 100:186404. [PMID: 18518399 DOI: 10.1103/physrevlett.100.186404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2007] [Indexed: 05/26/2023]
Abstract
We study a model of strongly interacting spinless fermions on an anisotropic triangular lattice. At half-filling and the limit of strong repulsive nearest-neighbor interactions, the fermions align in stripes and form an insulating state. When a particle is doped, it either follows a one-dimensional free motion along the stripes or fractionalizes perpendicular to the stripes. The two propagations yield a dimensional tuning of the electronic state. We study the stability of this phase and derive an effective model to describe the low-energy excitations. Spectral functions are presented which can be used to experimentally detect signatures of the charge excitations.
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Affiliation(s)
- Chisa Hotta
- Department of Physics, Faculty of Science, Kyoto Sangyo University, Kyoto 603-8555, Japan
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26
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Sen A, Dutt P, Damle K, Moessner R. Variational wave-function study of the triangular lattice supersolid. PHYSICAL REVIEW LETTERS 2008; 100:147204. [PMID: 18518069 DOI: 10.1103/physrevlett.100.147204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2008] [Indexed: 05/26/2023]
Abstract
We present a variational wave function which explains the behavior of the supersolid state formed by hard-core bosons on the triangular lattice. The wave function is a linear superposition of only and all configurations minimizing the repulsion between the bosons (which it thus implements as a hard constraint). Its properties can be evaluated exactly--in particular, the variational minimization of the energy yields (i) the surprising and initially controversial spontaneous density deviation from half-filling (ii) a quantitatively accurate estimate of the corresponding density wave (solid) order parameter.
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Affiliation(s)
- Arnab Sen
- Department of Theoretical Physics, Tata Institute of Fundamental Research, Mumbai 400005, India
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27
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Titvinidze I, Snoek M, Hofstetter W. Supersolid bose-fermi mixtures in optical lattices. PHYSICAL REVIEW LETTERS 2008; 100:100401. [PMID: 18352164 DOI: 10.1103/physrevlett.100.100401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2007] [Indexed: 05/26/2023]
Abstract
We study a mixture of strongly interacting bosons and spinless fermions with on-site repulsion in a three-dimensional optical lattice. For this purpose we develop and apply a generalized dynamical mean-field theory, which is exact in infinite dimensions and reliably describes the full range from weak to strong coupling. We restrict ourselves to half filling. For weak Bose-Fermi repulsion a supersolid forms, in which bosonic superfluidity coexists with charge-density wave order. For stronger interspecies repulsion the bosons become localized while the charge-density wave order persists. The system is unstable against phase separation for weak repulsion among the bosons.
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Affiliation(s)
- I Titvinidze
- Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität, 60438 Frankfurt am Main, Germany
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28
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Schmidt KP, Dorier J, Läuchli AM, Mila F. Supersolid phase induced by correlated hopping in spin-1/2 frustrated quantum magnets. PHYSICAL REVIEW LETTERS 2008; 100:090401. [PMID: 18352679 DOI: 10.1103/physrevlett.100.090401] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2007] [Revised: 10/25/2007] [Indexed: 05/26/2023]
Abstract
We show that correlated hopping of triplets, which is often the dominant source of kinetic energy in dimer-based frustrated quantum magnets, produces a remarkably strong tendency to form supersolid phases in a magnetic field. These phases are characterized by simultaneous modulation and ordering of the longitudinal and transverse magnetization, respectively. Using quantum Monte Carlo and a semiclassical approach for an effective hard-core boson model with nearest-neighbor repulsion on a square lattice, we prove, in particular, that a supersolid phase can exist even if the repulsion is not strong enough to stabilize an insulating phase at half-filling. Experimental implications for frustrated quantum antiferromagnets in a magnetic field at zero and finite temperature are discussed.
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Affiliation(s)
- K P Schmidt
- Institute of Theoretical Physics, Ecole Polytechnique Fédérale de Lausanne, CH 1015 Lausanne, Switzerland.
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29
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Sengupta P, Batista CD. Spin supersolid in an anisotropic spin-one Heisenberg chain. PHYSICAL REVIEW LETTERS 2007; 99:217205. [PMID: 18233248 DOI: 10.1103/physrevlett.99.217205] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Indexed: 05/25/2023]
Abstract
We consider an S=1 Heisenberg chain with strong exchange (Delta=J(z)/J(perpendicular)) and single-ion uniaxial anisotropy (D) in a magnetic field (B) along the symmetry axis. The low-energy spectrum is described by an effective S=1/2 XXZ model that acts on two different low-energy sectors for a finite range of fields. The vacuum of each sector exhibits Ising-like antiferromagnetic ordering coexisting with the finite spin stiffness obtained from the exact solution of the XXZ model. In this way, we demonstrate the existence of a spin supersolid phase. We also compute the full Delta-B quantum phase diagram using a quantum Monte Carlo method.
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Affiliation(s)
- P Sengupta
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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30
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Petrov DS, Astrakharchik GE, Papoular DJ, Salomon C, Shlyapnikov GV. Crystalline phase of strongly interacting fermi mixtures. PHYSICAL REVIEW LETTERS 2007; 99:130407. [PMID: 17930564 DOI: 10.1103/physrevlett.99.130407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2007] [Indexed: 05/25/2023]
Abstract
We show that the system of weakly bound molecules of heavy and light fermionic atoms is characterized by a long-range intermolecular repulsion and can undergo a gas-crystal quantum transition if the mass ratio exceeds a critical value. For the critical mass ratio above 100 obtained in our calculations, this crystalline order can be observed as a superlattice in an optical lattice for heavy atoms with a small filling factor. We also find that this novel system is sufficiently stable with respect to molecular relaxation into deep bound states and to the process of trimer formation.
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Affiliation(s)
- D S Petrov
- Laboratoire de Physique Théorique et Modèles Statistiques, CNRS, Université Paris Sud, 91405 Orsay, France
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31
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Dutta O, Kanamoto R, Meystre P. Fermionic stabilization and density-wave ground state of a polar condensate. PHYSICAL REVIEW LETTERS 2007; 99:110404. [PMID: 17930417 DOI: 10.1103/physrevlett.99.110404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Indexed: 05/25/2023]
Abstract
We examine the stability of a trapped dipolar condensate mixed with a single-component fermion gas at T=0. Whereas pure dipolar condensates with a small s-wave interaction are unstable even at small dipole-dipole interaction strength, we find that the admixture of fermions can significantly stabilize them, depending on the strength of the boson-fermion interaction. Within the stable regime we find a region where a ground state is characterized by a density wave along the soft trap direction.
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Affiliation(s)
- O Dutta
- Department of Physics and B2 Institute, The University of Arizona, Tucson, Arizona 85721, USA
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32
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Laflorencie N, Mila F. Quantum and thermal transitions out of the supersolid phase of a 2D quantum antiferromagnet. PHYSICAL REVIEW LETTERS 2007; 99:027202. [PMID: 17678251 DOI: 10.1103/physrevlett.99.027202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2007] [Indexed: 05/16/2023]
Abstract
We investigate the thermodynamic properties of a field-induced supersolid phase in a 2D quantum antiferromagnet model. Using quantum Monte Carlo simulations, a very rich phase diagram is mapped out in the temperature-magnetic-field plane, with an extended supersolid region where a diagonal (solid) order coexists with a finite XY spin stiffness (superfluid). The various quantum and thermal transitions out of the supersolid state are characterized. Experimental consequences in the context of field-induced magnetization plateau materials are briefly discussed.
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Affiliation(s)
- Nicolas Laflorencie
- Institute of Theoretical Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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33
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Yi S, Li T, Sun CP. Novel quantum phases of dipolar bose gases in optical lattices. PHYSICAL REVIEW LETTERS 2007; 98:260405. [PMID: 17678073 DOI: 10.1103/physrevlett.98.260405] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2007] [Indexed: 05/16/2023]
Abstract
We investigate the quantum phases of polarized dipolar bosons loaded into a two-dimensional square and three-dimensional cubic optical lattices. We show that the long-range and anisotropic nature of the dipole-dipole interaction induces a rich variety of quantum phases, including the supersolid and striped supersolid phases in two-dimensional lattices, and the layered supersolid phase in three-dimensional lattices.
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Affiliation(s)
- S Yi
- Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, 100080, People's Republic of China
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34
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Sengupta P, Batista CD. Field-induced supersolid phase in spin-one Heisenberg models. PHYSICAL REVIEW LETTERS 2007; 98:227201. [PMID: 17677874 DOI: 10.1103/physrevlett.98.227201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2006] [Revised: 03/26/2007] [Indexed: 05/16/2023]
Abstract
We use numerical methods to demonstrate that the phase diagram of S=1 Heisenberg models with uniaxial anisotropy contains an extended supersolid phase. We show that this Hamiltonian is a particular case of a more general and ubiquitous model that describes the low-energy spectrum of some isotropic and frustrated spin-dimer systems. This result is crucial for finding a spin supersolid state in real magnets.
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Affiliation(s)
- P Sengupta
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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35
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Kato Y, Suzuki T, Kawashima N. Modification of directed-loop algorithm for continuous space simulation of bosonic systems. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 75:066703. [PMID: 17677385 DOI: 10.1103/physreve.75.066703] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Indexed: 05/16/2023]
Abstract
We modify the directed-loop algorithm (DLA) to solve the problem that typically arises from large on-site interaction. The large on-site interaction is inevitable when one tries to simulate a Bose gas system in continuum by discretizing the space with small lattice spacings. While the efficiency of a straightforward application of DLA decreases as the mesh becomes finer, the performance of the new method does not depend on it except for the trivial factor due to the increase in the number of lattice points.
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Affiliation(s)
- Yasuyuki Kato
- Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa, Chiba 277-8581, Japan
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36
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Isakov SV, Wessel S, Melko RG, Sengupta K, Kim YB. Hard-core bosons on the kagome lattice: valence-bond solids and their quantum melting. PHYSICAL REVIEW LETTERS 2006; 97:147202. [PMID: 17155288 DOI: 10.1103/physrevlett.97.147202] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2006] [Indexed: 05/12/2023]
Abstract
Using large scale quantum Monte Carlo simulations and dual vortex theory, we analyze the ground state phase diagram of hard-core bosons on the kagome lattice with nearest-neighbor repulsion. In contrast with the case of a triangular lattice, no supersolid emerges for strong interactions. While a uniform superfluid prevails at half filling, two novel solid phases emerge at densities rho=1/3 and rho=2/3. These solids exhibit an only partial ordering of the bosonic density, allowing for local resonances on a subset of hexagons of the kagome lattice. We provide evidence for a weakly first-order phase transition at the quantum melting point between these solid phases and the superfluid.
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Affiliation(s)
- S V Isakov
- Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
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37
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Ng KK, Lee TK. Supersolid phase in spin dimer XXZ systems under a magnetic field. PHYSICAL REVIEW LETTERS 2006; 97:127204. [PMID: 17025995 DOI: 10.1103/physrevlett.97.127204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2006] [Indexed: 05/12/2023]
Abstract
Using the quantum Monte Carlo method, we study, under external magnetic fields, the ground state phase diagram of the two-dimensional spin S=1/2 dimer model with an anisotropic intraplane antiferromagnetic coupling. With the anisotropy 4 greater/approximately Delta greater/approximately 3, a supersolid phase characterized by a nonuniform Bose condensate density that breaks translational symmetry is found. The rich phase diagram also contains a checkerboard solid, an antiferromagnet in the z axis, and a superfluid phase formed by S(z)= +1 spin triplets which has a finite staggered magnetization in the in-plane direction. As we show, the model can be realized as a consequence of including the next nearest neighbor coupling among dimers and our results suggest that spin dimer systems may be an ideal model system to study the supersolid phase.
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Affiliation(s)
- Kwai-Kong Ng
- Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan
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38
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Damle K, Senthil T. Spin nematics and magnetization plateau transition in anisotropic kagome magnets. PHYSICAL REVIEW LETTERS 2006; 97:067202. [PMID: 17026197 DOI: 10.1103/physrevlett.97.067202] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2006] [Indexed: 05/12/2023]
Abstract
We study S=1 kagome antiferromagnets with an isotropic Heisenberg exchange J and strong easy-axis single-ion anisotropy D. For D>>J, the low-energy physics can be described by an effective S=1/2 XXZ model with antiferromagnetic Jz approximately J and ferromagnetic J perpendicular approximately J2/D. Exploiting this connection, we argue that nontrivial ordering into a "spin-nematic" occurs whenever D dominates over J, and discuss its experimental signatures. We also study a magnetic field induced transition to a magnetization plateau state at magnetization 1/3 which breaks lattice translation symmetry due to ordering of the Sz and occupies a lobe in the B/Jz-Jz/J perpendicular phase diagram.
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Affiliation(s)
- Kedar Damle
- Department of Theoretical Physics, Tata Institute of Fundamental Research, 1, Homi Bhabha Road, Colaba, Mumbai 400005, India
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39
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Zhao E, Paramekanti A. Excitations in correlated superfluids near a continuous transition into a supersolid. PHYSICAL REVIEW LETTERS 2006; 96:105303. [PMID: 16605753 DOI: 10.1103/physrevlett.96.105303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2005] [Indexed: 05/08/2023]
Abstract
We study a superfluid on a lattice close to a transition into a supersolid phase and show that a uniform superflow in the homogeneous superfluid can drive the roton gap to zero. This leads to supersolid order around the vortex core in the superfluid, with the size of the modulated pattern around the core being related to the bulk superfluid density and roton gap. We also study the electronic tunneling density of states for a uniform superconductor near a phase transition into a supersolid phase. Implications are considered for strongly correlated superconductors.
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Affiliation(s)
- Erhai Zhao
- Department of Physics, University of Toronto, Toronto, Ontario M5S-1A7, Canada
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40
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Boninsegni M, Prokof'ev N. Supersolid phase of hard-core bosons on a triangular lattice. PHYSICAL REVIEW LETTERS 2005; 95:237204. [PMID: 16384336 DOI: 10.1103/physrevlett.95.237204] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Indexed: 05/05/2023]
Abstract
We study properties of the supersolid phase observed for hard-core bosons on the triangular lattice near half-integer filling factor, and the phase diagram of the system at finite temperature. We find that the solid order is always of the (2m, -m, -m) with m changing discontinuously from positive to negative values at half filling, in contrast with phases observed for Ising spins in a transverse magnetic field. At finite temperature we find two intersecting second-order transition lines: one in the 3-state Potts universality class and the other of the Kosterlitz-Thouless type.
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Affiliation(s)
- Massimo Boninsegni
- Department of Physics, University of Alberta, Edmonton, Alberta T6G 2J1, Canada
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41
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Melko RG, Paramekanti A, Burkov AA, Vishwanath A, Sheng DN, Balents L. Supersolid order from disorder: hard-core bosons on the triangular lattice. PHYSICAL REVIEW LETTERS 2005; 95:127207. [PMID: 16197107 DOI: 10.1103/physrevlett.95.127207] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2005] [Indexed: 05/04/2023]
Abstract
We study the interplay of Mott localization, geometric frustration, and superfluidity for hard-core bosons with nearest-neighbor repulsion on the triangular lattice. For this model at half filling, we demonstrate that superfluidity survives for arbitrarily large repulsion, and that diagonal solid order emerges in the strongly correlated regime from an order-by-disorder mechanism. This is thus an unusual example of a stable supersolid phase of hard-core lattice bosons at a commensurate filling.
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Affiliation(s)
- R G Melko
- Department of Physics, University of California, Santa Barbara, California 93106, USA
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