1
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Seifert UFP, Willsher J, Drescher M, Pollmann F, Knolle J. Spin-Peierls instability of the U(1) Dirac spin liquid. Nat Commun 2024; 15:7110. [PMID: 39160157 PMCID: PMC11333588 DOI: 10.1038/s41467-024-51367-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Accepted: 08/03/2024] [Indexed: 08/21/2024] Open
Abstract
Quantum fluctuations can inhibit long-range ordering in frustrated magnets and potentially lead to quantum spin liquid (QSL) phases. A prime example are gapless QSLs with emergent U(1) gauge fields, which have been understood to be described in terms of quantum electrodynamics in 2+1 dimension (QED3). Despite several promising candidate materials, however, a complicating factor for their realisation is the presence of other degrees of freedom. In particular lattice distortions can act to relieve magnetic frustration, precipitating conventionally ordered states. In this work, we use field-theoretic arguments as well as extensive numerical simulations to show that the U(1) Dirac QSL on the triangular and kagome lattices exhibits a weak-coupling instability due to the coupling of monopoles of the emergent gauge field to lattice distortions, leading to valence-bond solid ordering. This generalises the spin-Peierls instability of one-dimensional quantum critical spin chains to two-dimensional algebraic QSLs. We study static distortions as well as quantum-mechanical phonons. Even in regimes where the QSL is stable, the singular spin-lattice coupling leads to marked temperature-dependent corrections to the phonon spectrum, which provide salient experimental signatures of spin fractionalisation. We discuss the coupling of QSLs to the lattice as a general tool for their discovery and characterisation.
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Affiliation(s)
- Urban F P Seifert
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA, USA.
- Institute for Theoretical Physics, University of Cologne, Cologne, Germany.
| | - Josef Willsher
- Technical University of Munich, TUM School of Natural Sciences, Physics Department, Garching, Germany.
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, München, Germany.
| | - Markus Drescher
- Technical University of Munich, TUM School of Natural Sciences, Physics Department, Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, München, Germany
| | - Frank Pollmann
- Technical University of Munich, TUM School of Natural Sciences, Physics Department, Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, München, Germany
| | - Johannes Knolle
- Technical University of Munich, TUM School of Natural Sciences, Physics Department, Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, München, Germany
- Blackett Laboratory, Imperial College London, London, United Kingdom
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2
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Herrera Romero R, Bastarrachea-Magnani MA. Phase and Amplitude Modes in the Anisotropic Dicke Model with Matter Interactions. ENTROPY (BASEL, SWITZERLAND) 2024; 26:574. [PMID: 39056936 PMCID: PMC11276390 DOI: 10.3390/e26070574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2024] [Revised: 06/29/2024] [Accepted: 07/01/2024] [Indexed: 07/28/2024]
Abstract
Phase and amplitude modes, also called polariton modes, are emergent phenomena that manifest across diverse physical systems, from condensed matter and particle physics to quantum optics. We study their behavior in an anisotropic Dicke model that includes collective matter interactions. We study the low-lying spectrum in the thermodynamic limit via the Holstein-Primakoff transformation and contrast the results with the semi-classical energy surface obtained via coherent states. We also explore the geometric phase for both boson and spin contours in the parameter space as a function of the phases in the system. We unveil novel phenomena due to the unique critical features provided by the interplay between the anisotropy and matter interactions. We expect our results to serve the observation of phase and amplitude modes in current quantum information platforms.
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Affiliation(s)
| | - Miguel Angel Bastarrachea-Magnani
- Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Av. Ferrocarril San Rafael Atlixco 186, Mexico City C.P. 09310, Mexico
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3
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Yang J, Suwa H, Meyers D, Zhang H, Horak L, Zhang Z, Karapetrova E, Kim JW, Ryan PJ, Dean MPM, Hao L, Liu J. Extraordinary Magnetic Response of an Anisotropic 2D Antiferromagnet via Site Dilution. NANO LETTERS 2023; 23:11409-11415. [PMID: 38095312 DOI: 10.1021/acs.nanolett.3c02470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2023]
Abstract
A prominent characteristic of 2D magnetic systems is the enhanced spin fluctuations, which reduce the ordering temperature. We report that a magnetic field of only 1000th of the Heisenberg superexchange interaction can induce a crossover, which for practical purposes is the effective ordering transition, at temperatures about 6 times the Néel transition in a site-diluted two-dimensional anisotropic quantum antiferromagnet. Such a strong magnetic response is enabled because the system directly enters the antiferromagnetically ordered state from the isotropic disordered state, skipping the intermediate anisotropic stage. The underlying mechanism is achieved on a pseudospin-half square lattice realized in the [(SrIrO3)1/(SrTiO3)2] superlattice thin film that is designed to linearly couple the staggered magnetization to external magnetic fields by virtue of the rotational symmetry-preserving Dzyaloshinskii-Moriya interaction. Our model analysis shows that the skipping of the anisotropic regime despite finite anisotropy is due to the enhanced isotropic fluctuations under moderate dilution.
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Affiliation(s)
- Junyi Yang
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Hidemaro Suwa
- Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
| | - Derek Meyers
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, United States
- Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Han Zhang
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Lukas Horak
- Department of Condensed Matter Physics, Charles University, Ke Karlovu 5, 12116 Prague, Czech Republic
| | - Zhan Zhang
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Evguenia Karapetrova
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Jong-Woo Kim
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Philip J Ryan
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
- School of Physical Sciences, Dublin City University, Dublin 9, Ireland
| | - Mark P M Dean
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Lin Hao
- Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei, Anhui 230031, China
| | - Jian Liu
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
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4
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Machado F, Demler EA, Yao NY, Chatterjee S. Quantum Noise Spectroscopy of Dynamical Critical Phenomena. PHYSICAL REVIEW LETTERS 2023; 131:070801. [PMID: 37656851 DOI: 10.1103/physrevlett.131.070801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Accepted: 06/12/2023] [Indexed: 09/03/2023]
Abstract
The transition between distinct phases of matter is characterized by the nature of fluctuations near the critical point. We demonstrate that noise spectroscopy can not only diagnose the presence of a phase transition, but can also determine fundamental properties of its criticality. In particular, by analyzing a scaling collapse of the decoherence profile, one can directly extract the critical exponents of the transition and identify its universality class. Our approach naturally captures the presence of conservation laws and distinguishes between classical and quantum phase transitions. In the context of quantum magnetism, our proposal complements existing techniques and provides a novel toolset optimized for interrogating two-dimensional magnetic materials.
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Affiliation(s)
- Francisco Machado
- ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - Eugene A Demler
- Institute for Theoretical Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Norman Y Yao
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - Shubhayu Chatterjee
- Department of Physics, University of California, Berkeley, California 94720, USA
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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5
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Cui Y, Liu L, Lin H, Wu KH, Hong W, Liu X, Li C, Hu Z, Xi N, Li S, Yu R, Sandvik AW, Yu W. Proximate deconfined quantum critical point in SrCu 2(BO 3)2. Science 2023:eadc9487. [PMID: 37228220 DOI: 10.1126/science.adc9487] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 05/12/2023] [Indexed: 05/27/2023]
Abstract
The deconfined quantum critical point (DQCP) represents a paradigm shift in quantum matter studies, presenting a "beyond Landau" scenario for order-order transitions. Its experimental realization, however, has remained elusive. Using high-pressure 11B nuclear magnetic resonance measurements on the quantum magnet SrCu[Formula: see text](BO[Formula: see text])[Formula: see text], we here demonstrate a magnetic-field induced plaquette-singlet to antiferromagnetic transition above [Formula: see text] GPa at a notably low temperature, [Formula: see text]K. First-order signatures of the transition weaken with increasing pressure, and we observe quantum critical scaling at the highest pressure, [Formula: see text] GPa. Supported by model calculations, we suggest that these observations can be explained by a proximate DQCP inducing critical quantum fluctuations and emergent O(3) symmetry of the order parameters. Our findings offer a concrete experimental platform for the investigation of the DQCP.
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Affiliation(s)
- Yi Cui
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, China
| | - Lu Liu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Huihang Lin
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, China
| | - Kai-Hsin Wu
- Department of Physics, Boston University, Boston, MA 02215, USA
| | - Wenshan Hong
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xuefei Liu
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, China
| | - Cong Li
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, China
| | - Ze Hu
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, China
| | - Ning Xi
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, China
| | - Shiliang Li
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, Graduate University of the Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Rong Yu
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, China
- Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education), Renmin University of China, Beijing 100872, China
| | - Anders W Sandvik
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Department of Physics, Boston University, Boston, MA 02215, USA
| | - Weiqiang Yu
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, China
- Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education), Renmin University of China, Beijing 100872, China
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6
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Assefa TA, Seaberg MH, Reid AH, Shen L, Esposito V, Dakovski GL, Schlotter W, Holladay B, Streubel R, Montoya SA, Hart P, Nakahara K, Moeller S, Kevan SD, Fischer P, Fullerton EE, Colocho W, Lutman A, Decker FJ, Sinha SK, Roy S, Blackburn E, Turner JJ. The fluctuation-dissipation measurement instrument at the Linac Coherent Light Source. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:083902. [PMID: 36050107 DOI: 10.1063/5.0091297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 06/30/2022] [Indexed: 06/15/2023]
Abstract
The development of new modes at x-ray free electron lasers has inspired novel methods for studying fluctuations at different energies and timescales. For closely spaced x-ray pulses that can be varied on ultrafast time scales, we have constructed a pair of advanced instruments to conduct studies targeting quantum materials. We first describe a prototype instrument built to test the proof-of-principle of resonant magnetic scattering using ultrafast pulse pairs. This is followed by a description of a new endstation, the so-called fluctuation-dissipation measurement instrument, which was used to carry out studies with a fast area detector. In addition, we describe various types of diagnostics for single-shot contrast measurements, which can be used to normalize data on a pulse-by-pulse basis and calibrate pulse amplitude ratios, both of which are important for the study of fluctuations in materials. Furthermore, we present some new results using the instrument that demonstrates access to higher momentum resolution.
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Affiliation(s)
- T A Assefa
- Stanford Institute for Materials and Energy Science, Stanford University and SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - M H Seaberg
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94720, USA
| | - A H Reid
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94720, USA
| | - L Shen
- Stanford Institute for Materials and Energy Science, Stanford University and SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - V Esposito
- Stanford Institute for Materials and Energy Science, Stanford University and SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - G L Dakovski
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94720, USA
| | - W Schlotter
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94720, USA
| | - B Holladay
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94720, USA
| | - R Streubel
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA and Physics Department, University of California Santa Cruz, Santa Cruz, California 95064, USA
| | - S A Montoya
- Center for Memory and Recording Research, University of California-San Diego, La Jolla, California 92093, USA
| | - P Hart
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94720, USA
| | - K Nakahara
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94720, USA
| | - S Moeller
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94720, USA
| | - S D Kevan
- Department of Physics, University of Oregon, Eugene, Oregon 97401, USA
| | - P Fischer
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA and Physics Department, University of California Santa Cruz, Santa Cruz, California 95064, USA
| | - E E Fullerton
- Center for Memory and Recording Research, University of California-San Diego, La Jolla, California 92093, USA
| | - W Colocho
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94720, USA
| | - A Lutman
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94720, USA
| | - F-J Decker
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94720, USA
| | - S K Sinha
- Department of Physics, University of California-San Diego, La Jolla, California 92093, USA
| | - S Roy
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - E Blackburn
- Division of Synchrotron Radiation Research, Department of Physics, Lund University, 22100 Lund, Sweden
| | - J J Turner
- Stanford Institute for Materials and Energy Science, Stanford University and SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
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7
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Yang S, Liu X, Li W, Yang J, Ying T, Li X, Sun X. Enhanced d-wave pairing in the two-dimensional Hubbard model with periodically modulated hopping amplitudes. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:375501. [PMID: 35790173 DOI: 10.1088/1361-648x/ac7e9c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 07/05/2022] [Indexed: 06/15/2023]
Abstract
Utilizing determinant quantum Monte Carlo algorithm, the evolution of thed-wave pairing in the Hubbard model on the square lattice tuned by the periodically modulated hopping amplitudes is studied. The hopping amplitudes are homogeneous in thexˆ-direction, while in theyˆ-direction the hopping amplitudes are modulated with periodP, wherety=t+dt,ty'=t-(P-1)dt, and the modulation periodPequals 2, 3 and 4 lattice spacings. The latter two modulation periods are motivated by the observation of period-3 and period-4 stripe order in cuprate superconductors. For all the periodsP, we find that the modulated hopping inhomogeneity enhances thed-wave pairing and an optimal inhomogeneity exists.
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Affiliation(s)
- Shuhui Yang
- Institute of Modern Optics, School of Physics, Harbin Institute of Technology, Harbin 150001, People's Republic of China
| | - Xingcan Liu
- Institute of Modern Optics, School of Physics, Harbin Institute of Technology, Harbin 150001, People's Republic of China
| | - Weiqi Li
- School of Physics, Harbin Institute of Technology, Harbin 150001, People's Republic of China
| | - Jianqun Yang
- School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, People's Republic of China
| | - Tao Ying
- Institute of Modern Optics, School of Physics, Harbin Institute of Technology, Harbin 150001, People's Republic of China
| | - Xingji Li
- School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, People's Republic of China
| | - Xiudong Sun
- Institute of Modern Optics, School of Physics, Harbin Institute of Technology, Harbin 150001, People's Republic of China
- Key Laboratory of Micro-Nano Optoelectronic Information System, Ministry of Industry and Information Technology, Harbin 150001, People's Republic of China
- Key Laboratory of Micro-Optics and Photonic Technology of Heilongjiang Province, Harbin Institute of Technology, Harbin 150001, People's Republic of China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, People's Republic of China
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8
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Decay and renormalization of a longitudinal mode in a quasi-two-dimensional antiferromagnet. Nat Commun 2021; 12:5331. [PMID: 34504075 PMCID: PMC8429660 DOI: 10.1038/s41467-021-25591-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 08/18/2021] [Indexed: 11/08/2022] Open
Abstract
An ongoing challenge in the study of quantum materials, is to reveal and explain collective quantum effects in spin systems where interactions between different modes types are important. Here we approach this problem through a combined experimental and theoretical study of interacting transverse and longitudinal modes in an easy-plane quantum magnet near a continuous quantum phase transition. Our inelastic neutron scattering measurements of Ba2FeSi2O7 reveal the emergence, decay, and renormalization of a longitudinal mode throughout the Brillouin zone. The decay of the longitudinal mode is particularly pronounced at the zone center. To account for the many-body effects of the interacting low-energy modes in anisotropic magnets, we generalize the standard spin-wave theory. The measured mode decay and renormalization is reproduced by including all one-loop corrections. The theoretical framework developed here is broadly applicable to quantum magnets with more than one type of low energy mode. Anisotropic spin S >1/2 quantum magnets can have multiple low energy modes. In this manuscript, the authors study the interaction of such low energy modes in the S = 1 antiferromagnet Ba2FeSi2O7 by combining neutron scattering measurements with an SU(3) generalization of the 1/S expansion.
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9
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Riedl K, Valentí R, Winter SM. Critical spin liquid versus valence-bond glass in a triangular-lattice organic antiferromagnet. Nat Commun 2019; 10:2561. [PMID: 31189897 PMCID: PMC6561973 DOI: 10.1038/s41467-019-10604-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 05/15/2019] [Indexed: 11/23/2022] Open
Abstract
In the quest for materials with unconventional quantum phases, the organic triangular-lattice antiferromagnet κ-(ET)2Cu2(CN)3 has been extensively discussed as a quantum spin liquid (QSL) candidate. The description of its low temperature properties has become, however, a particularly challenging task. Recently, an intriguing quantum critical behaviour was suggested from low-temperature magnetic torque experiments. Here we highlight significant deviations of the experimental observations from a quantum critical scenario by performing a microscopic analysis of all anisotropic contributions, including Dzyaloshinskii-Moriya and multi-spin scalar chiral interactions. Instead, we show that disorder-induced spin defects provide a comprehensive explanation of the low-temperature properties. These spins are attributed to valence bond defects that emerge spontaneously as the QSL enters a valence-bond glass phase at low temperature. This theoretical treatment is applicable to a general class of frustrated magnetic systems and has important implications for the interpretation of magnetic torque, nuclear magnetic resonance, thermal transport and thermodynamic experiments.
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Affiliation(s)
- Kira Riedl
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438, Frankfurt am Main, Germany.
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438, Frankfurt am Main, Germany
| | - Stephen M Winter
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438, Frankfurt am Main, Germany.
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10
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Schäfer T, Katanin AA, Kitatani M, Toschi A, Held K. Quantum Criticality in the Two-Dimensional Periodic Anderson Model. PHYSICAL REVIEW LETTERS 2019; 122:227201. [PMID: 31283298 DOI: 10.1103/physrevlett.122.227201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 04/10/2019] [Indexed: 06/09/2023]
Abstract
We study the phase diagram and quantum critical region of one of the fundamental models for electronic correlations: the periodic Anderson model. Employing the recently developed dynamical vertex approximation, we find a phase transition between a zero-temperature antiferromagnetic insulator and a Kondo insulator. In the quantum critical region, we determine a critical exponent γ=2 for the antiferromagnetic susceptibility. At higher temperatures, we have free spins with γ=1 instead, whereas at lower temperatures, there is an even stronger increase and suppression of the susceptibility below and above the quantum critical point, respectively.
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Affiliation(s)
- T Schäfer
- Institute of Solid State Physics, TU Wien, 1040 Vienna, Austria
- Collège de France, 11 place Marcelin Berthelot, 75005 Paris, France
- CPHT, CNRS, École Polytechnique, IP Paris, F-91128 Palaiseau, France
| | - A A Katanin
- Institute of Metal Physics, Kovalevskaya str. 18, 620990 Ekaterinburg, Russia
| | - M Kitatani
- Institute of Solid State Physics, TU Wien, 1040 Vienna, Austria
| | - A Toschi
- Institute of Solid State Physics, TU Wien, 1040 Vienna, Austria
| | - K Held
- Institute of Solid State Physics, TU Wien, 1040 Vienna, Austria
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11
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Turkeshi X, Mendes-Santos T, Giudici G, Dalmonte M. Entanglement-Guided Search for Parent Hamiltonians. PHYSICAL REVIEW LETTERS 2019; 122:150606. [PMID: 31050506 DOI: 10.1103/physrevlett.122.150606] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 09/26/2018] [Indexed: 06/09/2023]
Abstract
We introduce a method for the search of parent Hamiltonians of input wave functions based on the structure of their reduced density matrix. The two key elements of our recipe are an ansatz on the relation between the reduced density matrix and parent Hamiltonian that is exact at the field theory level, and a minimization procedure on the space of relative entropies, which is particularly convenient due to its convexity. As examples, we show how our method correctly reconstructs the parent Hamiltonian correspondent to several nontrivial ground state wave functions, including conformal and symmetry-protected-topological phases, and quantum critical points of two-dimensional antiferromagnets described by strongly coupled field theories. Our results show the entanglement structure of ground state wave functions considerably simplifies the search for parent Hamiltonians.
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Affiliation(s)
- X Turkeshi
- The Abdus Salam International Centre for Theoretical Physics, strada Costiera 11, 34151 Trieste, Italy
- SISSA, via Bonomea 265, 34136 Trieste, Italy
- INFN, sezione di Trieste, 34136 Trieste, Italy
| | - T Mendes-Santos
- The Abdus Salam International Centre for Theoretical Physics, strada Costiera 11, 34151 Trieste, Italy
| | - G Giudici
- The Abdus Salam International Centre for Theoretical Physics, strada Costiera 11, 34151 Trieste, Italy
- SISSA, via Bonomea 265, 34136 Trieste, Italy
- INFN, sezione di Trieste, 34136 Trieste, Italy
| | - M Dalmonte
- The Abdus Salam International Centre for Theoretical Physics, strada Costiera 11, 34151 Trieste, Italy
- SISSA, via Bonomea 265, 34136 Trieste, Italy
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12
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Reconstructing the quantum critical fan of strongly correlated systems using quantum correlations. Nat Commun 2019; 10:577. [PMID: 30718513 PMCID: PMC6362001 DOI: 10.1038/s41467-019-08324-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 12/12/2018] [Indexed: 11/09/2022] Open
Abstract
Albeit occurring at zero temperature, quantum critical phenomena have a huge impact on the finite-temperature phase diagram of strongly correlated systems, giving experimental access to their observation. Indeed, the existence of a gapless, zero-temperature quantum critical point induces the existence of an extended region in parameter space-the quantum critical fan (QCF)-characterized by power-law temperature dependences of all observables. Identifying experimentally the QCF and its crossovers to other regimes (renormalized classical, quantum disordered) remains nonetheless challenging. Focusing on paradigmatic models of quantum phase transitions, here we show that quantum correlations-captured by the quantum variance of the order parameter-exhibit the temperature scaling associated with the QCF over a parameter region much broader than that revealed by ordinary correlations. The link existing between the quantum variance and the dynamical susceptibility paves the way to an experimental reconstruction of the QCF using spectroscopic techniques.
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13
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Ma N, Weinberg P, Shao H, Guo W, Yao DX, Sandvik AW. Anomalous Quantum-Critical Scaling Corrections in Two-Dimensional Antiferromagnets. PHYSICAL REVIEW LETTERS 2018; 121:117202. [PMID: 30265096 DOI: 10.1103/physrevlett.121.117202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 07/24/2018] [Indexed: 06/08/2023]
Abstract
We study the Néel-paramagnetic quantum phase transition in two-dimensional dimerized S=1/2 Heisenberg antiferromagnets using finite-size scaling of quantum Monte Carlo data. We resolve the long-standing issue of the role of cubic interactions arising in the bond-operator representation when the dimer pattern lacks a certain symmetry. We find nonmonotonic (monotonic) size dependence in the staggered (columnar) dimerized model, where cubic interactions are (are not) present. We conclude that there is a new irrelevant field in the staggered model, but, at variance with previous claims, it is not the leading irrelevant field. The new exponent is ω_{2}≈1.25 and the prefactor of the correction L^{-ω_{2}} is large and comes with a different sign from that of the conventional correction with ω_{1}≈0.78. Our study highlights competing scaling corrections at quantum critical points.
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Affiliation(s)
- Nvsen Ma
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
- Beijing National Laboratory of Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Department of Physics, Boston University, Boston, Massachusetts 02215, USA
| | - Phillip Weinberg
- Department of Physics, Boston University, Boston, Massachusetts 02215, USA
| | - Hui Shao
- Department of Physics, Boston University, Boston, Massachusetts 02215, USA
- Beijing Computational Science Research Center, Beijing 100193, China
| | - Wenan Guo
- Beijing Computational Science Research Center, Beijing 100193, China
- Department of Physics, Beijing Normal University, Beijing 100084, China
| | - Dao-Xin Yao
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Anders W Sandvik
- Beijing National Laboratory of Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Department of Physics, Boston University, Boston, Massachusetts 02215, USA
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14
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Schecter M, Syljuåsen OF, Paaske J. Nematic Bond Theory of Heisenberg Helimagnets. PHYSICAL REVIEW LETTERS 2017; 119:157202. [PMID: 29077464 DOI: 10.1103/physrevlett.119.157202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Indexed: 06/07/2023]
Abstract
We study classical two-dimensional frustrated Heisenberg models with generically incommensurate ground states. A new theory for the lattice-nematic "order by disorder" transition is developed based on the self-consistent determination of the effective exchange coupling bonds. In our approach, fluctuations of the constraint field imposing conservation of the local magnetic moment drive nematicity at low temperatures. The critical temperature is found to be highly sensitive to the peak helimagnetic wave vector, and vanishes continuously when approaching rotation symmetric Lifshitz points. Transitions between symmetry distinct nematic orders may occur by tuning the exchange parameters, leading to lines of bicritical points.
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Affiliation(s)
- Michael Schecter
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Olav F Syljuåsen
- Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
| | - Jens Paaske
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
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15
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Mazurenko A, Chiu CS, Ji G, Parsons MF, Kanász-Nagy M, Schmidt R, Grusdt F, Demler E, Greif D, Greiner M. A cold-atom Fermi–Hubbard antiferromagnet. Nature 2017; 545:462-466. [DOI: 10.1038/nature22362] [Citation(s) in RCA: 419] [Impact Index Per Article: 59.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 04/03/2017] [Indexed: 11/09/2022]
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16
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Qin YQ, Normand B, Sandvik AW, Meng ZY. Amplitude Mode in Three-Dimensional Dimerized Antiferromagnets. PHYSICAL REVIEW LETTERS 2017; 118:147207. [PMID: 28430475 DOI: 10.1103/physrevlett.118.147207] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Indexed: 06/07/2023]
Abstract
The amplitude ("Higgs") mode is a ubiquitous collective excitation related to spontaneous breaking of a continuous symmetry. We combine quantum Monte Carlo (QMC) simulations with stochastic analytic continuation to investigate the dynamics of the amplitude mode in a three-dimensional dimerized quantum spin system. We characterize this mode by calculating the spin and dimer spectral functions on both sides of the quantum critical point, finding that both the energies and the intrinsic widths of the excitations satisfy field-theoretical scaling predictions. While the line width of the spin response is close to that observed in neutron scattering experiments on TlCuCl_{3}, the dimer response is significantly broader. Our results demonstrate that highly nontrivial dynamical properties are accessible by modern QMC and analytic continuation methods.
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Affiliation(s)
- Yan Qi Qin
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - B Normand
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Anders W Sandvik
- Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
| | - Zi Yang Meng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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17
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Lucas A, Gazit S, Podolsky D, Witczak-Krempa W. Dynamical Response near Quantum Critical Points. PHYSICAL REVIEW LETTERS 2017; 118:056601. [PMID: 28211720 DOI: 10.1103/physrevlett.118.056601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Indexed: 06/06/2023]
Abstract
We study high-frequency response functions, notably the optical conductivity, in the vicinity of quantum critical points (QCPs) by allowing for both detuning from the critical coupling and finite temperature. We consider general dimensions and dynamical exponents. This leads to a unified understanding of sum rules. In systems with emergent Lorentz invariance, powerful methods from quantum field theory allow us to fix the high-frequency response in terms of universal coefficients. We test our predictions analytically in the large-N O(N) model and using the gauge-gravity duality and numerically via quantum Monte Carlo simulations on a lattice model hosting the interacting superfluid-insulator QCP. In superfluid phases, interacting Goldstone bosons qualitatively change the high-frequency optical conductivity and the corresponding sum rule.
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Affiliation(s)
- Andrew Lucas
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Physics, Stanford University, Stanford, California 94305, USA
| | - Snir Gazit
- Department of Physics, University of California, Berkeley, Berkeley, California 94720, USA
| | | | - William Witczak-Krempa
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Département de Physique, Université de Montréal, Montréal (Québec), H3C 3J7, Canada
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18
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Shimizu Y, Hiramatsu T, Maesato M, Otsuka A, Yamochi H, Ono A, Itoh M, Yoshida M, Takigawa M, Yoshida Y, Saito G. Pressure-Tuned Exchange Coupling of a Quantum Spin Liquid in the Molecular Triangular Lattice κ-(ET)_{2}Ag_{2}(CN)_{3}. PHYSICAL REVIEW LETTERS 2016; 117:107203. [PMID: 27636491 DOI: 10.1103/physrevlett.117.107203] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Indexed: 06/06/2023]
Abstract
The effects of pressure on a quantum spin liquid are investigated in an organic Mott insulator κ-(ET)_{2}Ag_{2}(CN)_{3} with a spin-1/2 triangular lattice. The application of negative chemical pressure to κ-(ET)_{2}Cu_{2}(CN)_{3}, which is a well-known sister Mott insulator, allows for extensive tuning of antiferromagnetic exchange coupling, with J/k_{B}=175-310 K, under hydrostatic pressure. Based on ^{13}C nuclear magnetic resonance measurements under pressure, we uncover universal scaling in the static and dynamic spin susceptibilities down to low temperatures ∼0.1k_{B}T/J. The persistent fluctuations and residual specific heat coefficient are consistent with the presence of gapless low-lying excitations. Our results thus demonstrate the fundamental finite-temperature properties of a quantum spin liquid in a wide parameter range.
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Affiliation(s)
- Yasuhiro Shimizu
- Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602, Japan
| | - Takaaki Hiramatsu
- Faculty of Agriculture, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan
| | - Mitsuhiko Maesato
- Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Akihiro Otsuka
- Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
- Research Center for Low Temperature and Materials Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Hideki Yamochi
- Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
- Research Center for Low Temperature and Materials Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Akihiro Ono
- Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602, Japan
| | - Masayuki Itoh
- Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602, Japan
| | - Makoto Yoshida
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Masashi Takigawa
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Yukihiro Yoshida
- Faculty of Agriculture, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan
| | - Gunzi Saito
- Faculty of Agriculture, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan
- Toyota Physical and Chemical Research Institute, Nagakute, Aichi 480-1192, Japan
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19
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Shao H, Guo W, Sandvik AW. Quantum criticality with two length scales. Science 2016; 352:213-6. [DOI: 10.1126/science.aad5007] [Citation(s) in RCA: 132] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 03/01/2016] [Indexed: 11/02/2022]
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20
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Witczak-Krempa W. Constraining quantum critical dynamics: (2+1)D Ising model and beyond. PHYSICAL REVIEW LETTERS 2015; 114:177201. [PMID: 25978256 DOI: 10.1103/physrevlett.114.177201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Indexed: 06/04/2023]
Abstract
Quantum critical (QC) phase transitions generally lead to the absence of quasiparticles. The resulting correlated quantum fluid, when thermally excited, displays rich universal dynamics. We establish nonperturbative constraints on the linear-response dynamics of conformal QC systems at finite temperature, in spatial dimensions above 1. Specifically, we analyze the large frequency or momentum asymptotics of observables, which we use to derive powerful sum rules and inequalities. The general results are applied to the O(N) Wilson-Fisher fixed point, describing the QC Ising model when N=1. We focus on the order parameter and scalar susceptibilities, and the dynamical shear viscosity. Connections to simulations, experiments, and gauge theories are made.
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21
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Sun F, Yu XL, Ye J, Fan H, Liu WM. Topological quantum phase transition in synthetic non-Abelian gauge potential: gauge invariance and experimental detections. Sci Rep 2014; 3:2119. [PMID: 23846153 PMCID: PMC3709414 DOI: 10.1038/srep02119] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 06/13/2013] [Indexed: 11/16/2022] Open
Abstract
The method of synthetic gauge potentials opens up a new avenue for our understanding and discovering novel quantum states of matter. We investigate the topological quantum phase transition of Fermi gases trapped in a honeycomb lattice in the presence of a synthetic non-Abelian gauge potential. We develop a systematic fermionic effective field theory to describe a topological quantum phase transition tuned by the non-Abelian gauge potential and explore its various important experimental consequences. Numerical calculations on lattice scales are performed to compare with the results achieved by the fermionic effective field theory. Several possible experimental detection methods of topological quantum phase transition are proposed. In contrast to condensed matter experiments where only gauge invariant quantities can be measured, both gauge invariant and non-gauge invariant quantities can be measured by experimentally generating various non-Abelian gauges corresponding to the same set of Wilson loops.
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Affiliation(s)
- Fadi Sun
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
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22
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Grover T. Entanglement monotonicity and the stability of gauge theories in three spacetime dimensions. PHYSICAL REVIEW LETTERS 2014; 112:151601. [PMID: 24785027 DOI: 10.1103/physrevlett.112.151601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Indexed: 06/03/2023]
Abstract
We employ the recent results on the generalization of the central charge theorem to three spacetime dimensions to derive nonperturbative results for several strongly interacting quantum field theories, including quantum electrodynamics (QED-3), and the theory corresponding to certain quantum phase transitions in condensed matter systems. In particular, by demanding that the universal constant part of the entanglement entropy decreases along the renormalization group flow (F theorem), we find sufficient conditions for the stability of QED-3 against chiral symmetry breaking and confinement. Using similar ideas, we derive strong constraints on the nature of quantum critical points in condensed matter systems with topological order.
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Affiliation(s)
- Tarun Grover
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA
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23
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Goldstone and Higgs modes of photons inside a cavity. Sci Rep 2013; 3:3476. [PMID: 24327105 PMCID: PMC3858793 DOI: 10.1038/srep03476] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Accepted: 11/25/2013] [Indexed: 11/30/2022] Open
Abstract
Goldstone and Higgs modes have been detected in various condensed matter, cold atom and particle physics experiments. Here, we demonstrate that the two modes can also be observed in optical systems with only a few (artificial) atoms inside a cavity. We establish this connection by studying the U(1)/Z2 Dicke model where N qubits (atoms) coupled to a single photon mode. We determine the Goldstone and Higgs modes inside the super-radiant phase and their corresponding spectral weights by performing both 1/J = 2/N expansion and exact diagonalization (ED) study at a finite N. We find nearly perfect agreements between the results achieved by the two approaches when N gets down even to N = 2. The quantum finite size effects at a few qubits make the two modes quite robust against an effectively small counterrotating wave term. We present a few schemes to reduce the critical coupling strength, so the two modes can be observed in several current available experimental systems by just conventional optical measurements.
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24
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Feng HT, Zhou YQ, Yin PL, Zong HS. Staggered spin susceptibility and chiral phase transition in thermalQED3. Int J Clin Exp Med 2013. [DOI: 10.1103/physrevd.88.125022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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25
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Yasuda S, Todo S. Monte Carlo simulation with aspect-ratio optimization: anomalous anisotropic scaling in dimerized antiferromagnets. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:061301. [PMID: 24483379 DOI: 10.1103/physreve.88.061301] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Indexed: 06/03/2023]
Abstract
We present a method that optimizes the aspect ratio of a spatially anisotropic quantum lattice model during the quantum Monte Carlo simulation, and realizes the virtually isotropic lattice automatically. The anisotropy is removed by using the Robbins-Monro algorithm based on the correlation length in each direction. The method allows for comparing directly the value of the critical amplitude among different anisotropic models, and identifying the universality more precisely. We apply our method to the staggered dimer antiferromagnetic Heisenberg model and demonstrate that the apparent nonuniversal behavior is attributed mainly to the strong size correction of the effective aspect ratio due to the existence of the cubic interaction.
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Affiliation(s)
- Shinya Yasuda
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Synge Todo
- Institute for Solid State Physics, University of Tokyo, 7-1-26-R501 Port Island South, Kobe 650-0047, Japan
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26
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Calder S, Giblin SR, Parker DR, Deen PP, Ritter C, Stewart JR, Rols S, Fennell T. Neutron scattering and μSR investigations of the low temperature state of LuCuGaO₄. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:356002. [PMID: 23917326 DOI: 10.1088/0953-8984/25/35/356002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
LuCuGaO₄ has magnetic Cu(2+) and diamagnetic Ga(3+) ions distributed on a triangular bilayer and is suggested to undergo a spin glass transition at Tg ∼ 0.4 K. Using μSR (muon spin rotation) and neutron scattering measurements, we show that at low temperature the spins form a short range correlated state with spin fluctuations detectable over a wide range of timescales: at 0.05 K magnetic fluctuations can be detected in both the μSR time window and also extending beyond 7 meV in the inelastic neutron scattering response, indicating magnetic fluctuations spanning timescales between ∼10(-5) and ∼10(-10) s. The dynamical susceptibility scales according to the form χ″(ω)T(α), with α = 1, throughout the measured temperature range (0.05-50 K). These effects are associated with quantum fluctuations and some degree of structural disorder in ostensibly quite different materials, including certain heavy fermion alloys, kagome spin liquids, quantum spin glasses, and valence bond glasses. We therefore suggest that LuCuGaO₄ is an interesting model compound for the further examination of disorder and quantum magnetism.
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Affiliation(s)
- S Calder
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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27
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Rançon A, Kodio O, Dupuis N, Lecheminant P. Thermodynamics in the vicinity of a relativistic quantum critical point in 2+1 dimensions. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:012113. [PMID: 23944420 DOI: 10.1103/physreve.88.012113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Indexed: 06/02/2023]
Abstract
We study the thermodynamics of the relativistic quantum O(N) model in two space dimensions. In the vicinity of the zero-temperature quantum critical point (QCP), the pressure can be written in the scaling form P(T)=P(0)+N(T(3)/c(2))F(N)(Δ/T), where c is the velocity of the excitations at the QCP and |Δ| a characteristic zero-temperature energy scale. Using both a large-N approach to leading order and the nonperturbative renormalization group, we compute the universal scaling function F(N). For small values of N (N</~10) we find that F(N)(x) is nonmonotonic in the quantum critical regime (|x|</~1) with a maximum near x=0. The large-N approach-if properly interpreted-is a good approximation both in the renormalized classical (x</~-1) and quantum disordered (x>/~1) regimes, but fails to describe the nonmonotonic behavior of F(N) in the quantum critical regime. We discuss the renormalization-group flows in the various regimes near the QCP and make the connection with the quantum nonlinear sigma model in the renormalized classical regime. We compute the Berezinskii-Kosterlitz-Thouless transition temperature in the quantum O(2) model and find that in the vicinity of the QCP the universal ratio T(BKT)/ρ(s)(0) is very close to π/2, implying that the stiffness ρ(s)(T(BKT)(-)) at the transition is only slightly reduced with respect to the zero-temperature stiffness ρ(s)(0). Finally, we briefly discuss the experimental determination of the universal function F(2) from the pressure of a Bose gas in an optical lattice near the superfluid-Mott-insulator transition.
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Affiliation(s)
- A Rançon
- James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
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28
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Pathak AK, Paudyal D, Mudryk Y, Gschneidner KA, Pecharsky VK. Anomalous Schottky specific heat and structural distortion in ferromagnetic PrAl2. PHYSICAL REVIEW LETTERS 2013; 110:186405. [PMID: 23683228 DOI: 10.1103/physrevlett.110.186405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Indexed: 06/02/2023]
Abstract
Unique from other rare earth dialuminides, PrAl(2) undergoes a cubic to tetragonal distortion below T = 30 K in a zero magnetic field, but the system recovers its cubic symmetry upon the application of an external magnetic field of 10 kOe via a lifting of the 4f crystal field splitting. The nuclear Schottky specific heat in PrAl(2) is anomalously high compared to that of pure Pr metal. First principles calculations reveal that the 4f crystal field splitting in the tetragonally distorted phase of PrAl(2) underpins the observed unusual low temperature phenomena.
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Affiliation(s)
- Arjun K Pathak
- The Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011-3020, USA.
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29
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Chen K, Liu L, Deng Y, Pollet L, Prokof'ev N. Universal properties of the Higgs resonance in (2+1)-dimensional U(1) critical systems. PHYSICAL REVIEW LETTERS 2013; 110:170403. [PMID: 23679688 DOI: 10.1103/physrevlett.110.170403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 02/07/2013] [Indexed: 06/02/2023]
Abstract
We present spectral functions for the magnitude squared of the order parameter in the scaling limit of the two-dimensional superfluid to Mott insulator quantum phase transition at constant density, which has emergent particle-hole symmetry and Lorentz invariance. The universal functions for the superfluid, Mott insulator, and normal liquid phases reveal a low-frequency resonance which is relatively sharp and is followed by a damped oscillation (in the first two phases only) before saturating to the quantum critical plateau. The counterintuitive resonance feature in the insulating and normal phases calls for deeper understanding of collective modes in the strongly coupled (2+1)-dimensional relativistic field theory. Our results are derived from analytically continued correlation functions obtained from path-integral Monte Carlo simulations of the Bose-Hubbard model.
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Affiliation(s)
- Kun Chen
- National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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30
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Endres M, Fukuhara T, Pekker D, Cheneau M, Schauβ P, Gross C, Demler E, Kuhr S, Bloch I. The ‘Higgs’ amplitude mode at the two-dimensional superfluid/Mott insulator transition. Nature 2012; 487:454-8. [DOI: 10.1038/nature11255] [Citation(s) in RCA: 241] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Accepted: 05/16/2012] [Indexed: 11/10/2022]
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31
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Pollet L, Prokof'ev N. Higgs mode in a two-dimensional superfluid. PHYSICAL REVIEW LETTERS 2012; 109:010401. [PMID: 23031091 DOI: 10.1103/physrevlett.109.010401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Indexed: 06/01/2023]
Abstract
We present solid evidence for the existence of a well-defined Higgs amplitude mode in two-dimensional relativistic field theories based on analytically continued results from quantum Monte Carlo simulations of the Bose-Hubbard model in the vicinity of the superfluid-Mott insulator quantum critical point, featuring emergent particle-hole symmetry and Lorentz invariance. The Higgs boson, seen as a well-defined low-frequency resonance in the spectral density, is quickly pushed to high energies in the superfluid phase and disappears by merging with the broad secondary peak at the characteristic interaction scale. Simulations of a trapped system of ultracold (87)Rb atoms demonstrate that the low-frequency resonance is lost for typical experimental parameters, while the characteristic frequency for the onset of a strong response is preserved.
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Affiliation(s)
- L Pollet
- Department of Physics and Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität München, D-80333 München, Germany
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32
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Sandvik AW, Kotov VN, Sushkov OP. Thermodynamics of a gas of deconfined bosonic spinons in two dimensions. PHYSICAL REVIEW LETTERS 2011; 106:207203. [PMID: 21668260 DOI: 10.1103/physrevlett.106.207203] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Revised: 04/05/2011] [Indexed: 05/30/2023]
Abstract
We consider the quantum phase transition between a Néel antiferromagnet and a valence-bond solid (VBS) in a two-dimensional system of S = 1/2 spins. Assuming that the excitations of the critical ground state are linearly dispersing deconfined spinons obeying Bose statistics, we derive expressions for the specific heat C and the magnetic susceptibility χ at low temperature T in terms of a correlation length ξ(T). Comparing with quantum Monte Carlo results for the J-Q model, which is a candidate for a deconfined Néel-VBS transition, we obtain an almost perfect consistency between C, χ, and ξ. The corresponding expressions for magnon (triplet) excitations are not internally consistent, however, lending strong support for spinon excitations in the J-Q model.
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Affiliation(s)
- Anders W Sandvik
- Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
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33
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Condensed Matter and AdS/CFT. FROM GRAVITY TO THERMAL GAUGE THEORIES: THE ADS/CFT CORRESPONDENCE 2011. [DOI: 10.1007/978-3-642-04864-7_9] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
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34
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Guarise M, Dalla Piazza B, Moretti Sala M, Ghiringhelli G, Braicovich L, Berger H, Hancock JN, van der Marel D, Schmitt T, Strocov VN, Ament LJP, van den Brink J, Lin PH, Xu P, Rønnow HM, Grioni M. Measurement of magnetic excitations in the two-dimensional antiferromagnetic Sr₂CuO₂Cl₂ insulator using resonant x-ray scattering: evidence for extended interactions. PHYSICAL REVIEW LETTERS 2010; 105:157006. [PMID: 21230933 DOI: 10.1103/physrevlett.105.157006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Indexed: 05/30/2023]
Abstract
We measured the momentum dependence of magnetic excitations in the model spin-1/2 2D antiferromagnetic insulator Sr2CuO2Cl2 (SCOC). We identify a single-spin-wave feature and a multimagnon continuum, with different polarization dependences. The spin waves display a large (70 meV) dispersion between the zone-boundary points (π, 0) and (π/2, π/2). Employing an extended t-t'-t''-U one-band Hubbard model, we find significant electronic hopping beyond nearest-neighbor Cu ions, indicative of extended magnetic interactions. The spectral line shape at (π, 0) indicates sizable quantum effects in SCOC and probably more generally in the cuprates.
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Affiliation(s)
- M Guarise
- Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015, Switzerland
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35
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Kotov VN, Oitmaa J, Sushkov O, Weihong Z. Spontaneous dimer order, excitation spectrum and quantum-phase transitions in the J1-J2 Heisenberg model. ACTA ACUST UNITED AC 2009. [DOI: 10.1080/13642810008208579] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Valeri N. Kotov
- a Department of Physics , University of Florida , Gainesville , Florida 32611-8440 , USA
| | - Jaan Oitmaa
- b School of Physics , University of New South Wales , Sydney 2052 , Australia
| | - Oleg Sushkov
- b School of Physics , University of New South Wales , Sydney 2052 , Australia
| | - Zheng Weihong
- b School of Physics , University of New South Wales , Sydney 2052 , Australia
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36
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Qi Y, Xu C, Sachdev S. Dynamics and transport of the Z2 spin liquid: application to kappa-(ET)2Cu2(CN)3. PHYSICAL REVIEW LETTERS 2009; 102:176401. [PMID: 19518801 DOI: 10.1103/physrevlett.102.176401] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2008] [Indexed: 05/27/2023]
Abstract
We describe neutron scattering, NMR relaxation, and thermal transport properties of Z2 spin liquids in two dimensions. Comparison to recent experiments on the spin S=1/2 triangular lattice antiferromagnet in kappa-(ET)2Cu2(CN)3 shows that this compound may realize a Z2 spin liquid. We argue that the topological "vison" excitations dominate thermal transport, and that recent thermal conductivity experiments by M. Yamashita et al. have observed the vison gap.
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Affiliation(s)
- Yang Qi
- Department of Physics, Harvard University, Cambridge Massachusetts 02138, USA
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37
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Wenzel S, Bogacz L, Janke W. Evidence for an unconventional universality class from a two-dimensional dimerized quantum heisenberg model. PHYSICAL REVIEW LETTERS 2008; 101:127202. [PMID: 18851407 DOI: 10.1103/physrevlett.101.127202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Revised: 07/10/2008] [Indexed: 05/26/2023]
Abstract
The two-dimensional J-J' dimerized quantum Heisenberg model is studied on the square lattice by means of (stochastic series expansion) quantum Monte Carlo simulations as a function of the coupling ratio alpha=J'/J. The critical point of the order-disorder quantum phase transition in the J-J' model is determined as alpha_c=2.5196(2) by finite-size scaling for up to approximately 10 000 quantum spins. By comparing six dimerized models we show, contrary to the current belief, that the critical exponents of the J-J' model are not in agreement with the three-dimensional classical Heisenberg universality class. This lends support to the notion of nontrivial critical excitations at the quantum critical point.
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Affiliation(s)
- Sandro Wenzel
- Institut für Theoretische Physik and Centre for Theoretical Sciences (NTZ), Universität Leipzig, Leipzig, Germany.
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38
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Quantum phases and phase transitions of Mott insulators. ACTA ACUST UNITED AC 2008. [DOI: 10.1007/bfb0119599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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39
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Xu C, Sachdev S. Square-lattice algebraic spin liquid with SO(5) symmetry. PHYSICAL REVIEW LETTERS 2008; 100:137201. [PMID: 18517992 DOI: 10.1103/physrevlett.100.137201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2007] [Indexed: 05/26/2023]
Abstract
We propose a critical spin liquid ground state for S=1/2 antiferromagnets on the square lattice. In a renormalization group analysis of the "staggered flux" algebraic spin liquid, we examine perturbations, present in the antiferromagnet, which break its global SU(4) symmetry to SO(5). At physical parameter values, we find an instability towards a fixed point with SO(5) symmetry. We discuss the possibility that this fixed point describes a transition between the Néel and valence bond solid states, and the relationship to the SO(5) nonlinear sigma model of Tanaka and Hu.
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Affiliation(s)
- Cenke Xu
- Department of Physics, Harvard University, Cambridge Massachusetts 02138, USA
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40
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Melko RG, Kaul RK. Scaling in the fan of an unconventional quantum critical point. PHYSICAL REVIEW LETTERS 2008; 100:017203. [PMID: 18232812 DOI: 10.1103/physrevlett.100.017203] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Revised: 10/08/2007] [Indexed: 05/25/2023]
Abstract
We present results of extensive finite-temperature quantum Monte Carlo simulations on a SU(2) symmetric S=1/2 quantum antiferromagnet with four-spin interaction [A. W. Sandvik, Phys. Rev. Lett. 98, 227202 (2007)10.1103/PhysRevLett.98.227202]. Our simulations, which are free of the sign problem and carried out on lattices containing in excess of 1.6 x 10(4) spins, indicate that the four-spin interaction destroys the Néel order at an unconventional z = 1 quantum critical point, producing a valence-bond solid paramagnet. Our results are consistent with the "deconfined quantum criticality" scenario.
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Affiliation(s)
- Roger G Melko
- Department of Physics and Astronomy, University of Waterloo, Ontario, N2L 3G1, Canada
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41
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Nazario Z, Santiago DI. Elementary excitations of quantum critical (2+1)-dimensional antiferromagnets. PHYSICAL REVIEW LETTERS 2006; 97:197201. [PMID: 17155655 DOI: 10.1103/physrevlett.97.197201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Revised: 04/14/2006] [Indexed: 05/12/2023]
Abstract
It has been proposed that there are degrees of freedom intrinsic to quantum critical points that can contribute to quantum critical physics. We point out that this conclusion is quite general below the upper critical dimension. We show that in (2+1)D antiferromagnets Skyrmion excitations are stable at criticality and identify them as the critical excitations. We find exact solutions composed of Skyrmion and anti-Skyrmion superpositions, which we call topolons. We include the topolons in the partition function and renormalize by integrating out small size topolons and short wavelength spin waves. We obtain a correlation length exponent nu=0.690 666 and anomalous dimension eta=0.0166.
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Affiliation(s)
- Zaira Nazario
- Department of Physics, Stanford University, Stanford, CA 94305, USA
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42
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Barzykin V, Pines D. Phenomenological model of protected behavior in the pseudogap state of underdoped cuprate superconductors. PHYSICAL REVIEW LETTERS 2006; 96:247002. [PMID: 16907271 DOI: 10.1103/physrevlett.96.247002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2006] [Indexed: 05/11/2023]
Abstract
By extending previous work on the scaling of low frequency magnetic properties of the 2-1-4 cuprates to the 1-2-3 materials, we arrive at a consistent phenomenological description of protected behavior in the pseudogap state of the magnetically underdoped cuprates. Between zero hole doping and a doping level of approximately 0.22, it reflects the presence of a mixture of an insulating spin liquid that produces the measured magnetic scaling behavior and a Fermi liquid that becomes superconducting for doping levels x>0.06. Our analysis suggests the existence of two quantum critical points, at doping levels x approximately 0.05 and x approximately 0.22, and that d-wave superconductivity in the pseudogap region arises from quasiparticle-spin liquid interaction, i.e., magnetic interactions between quasiparticles in the Fermi liquid induced by their coupling to the spin liquid excitations.
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Affiliation(s)
- Victor Barzykin
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
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43
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Sandvik AW. Quantum criticality and percolation in dimer-diluted two-dimensional antiferromagnets. PHYSICAL REVIEW LETTERS 2006; 96:207201. [PMID: 16803199 DOI: 10.1103/physrevlett.96.207201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2006] [Indexed: 05/10/2023]
Abstract
The S = 1/2 Heisenberg model is considered on bilayer and single-layer square lattices with couplings J1, J2, with each spin belonging to one J2-coupled dimer. A transition from a Néel to disordered ground state occurs at a critical value of g = J2/J1. The systems are here studied at their dimer-dilution percolation points p*. The multicritical point (g*,p*) previously found for the bilayer is not reproduced for the single layer. Instead, there is a line of critical points (g < g*, p*) with continuously varying exponents. The uniform magnetic susceptibility diverges as T(-alpha) with alpha element of [1/2,1]. This unusual behavior is attributed to an effective free-moment density approximately T(1-alpha). The susceptibility of the bilayer is not divergent but exhibits remarkably robust quantum-critical scaling.
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Affiliation(s)
- Anders W Sandvik
- Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
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44
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Dai J, Zhang WM. Quantum nonlinear sigma model for arbitrary spin Heisenberg antiferromagnets. PHYSICAL REVIEW LETTERS 2005; 95:167205. [PMID: 16241840 DOI: 10.1103/physrevlett.95.167205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Indexed: 05/05/2023]
Abstract
We derive a quantum nonlinear sigma model (QNLSM) for quantum Heisenberg antiferromagnets (QHA) with arbitrary S (spin) values. A upper limit of the low temperature is naturally carried out for the reliability of the QNLSM. The S dependence of the effective coupling constant and the spin-wave velocity in the QNLSM are also obtained explicitly. The resulting spin-wave velocity for 2D spin-1/2 QHA highly concurs with the experimental data of high T(c) compound La(2)CuO(4). The predicted correlation lengths for 2D QHA and spin-gap magnitudes for 1D QHA also agrees with the accurate numerical results.
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Affiliation(s)
- Jianhui Dai
- Zhejiang Institute of Modern Physics, Zhejiang University, Hangzhou, China
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45
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Honda Z, Katsumata K, Kikkawa A, Yamada K. Thermodynamic properties in the approach to the quantum critical point of the spin-ladder material Na2Co2(C2O4)3(H2O)2. PHYSICAL REVIEW LETTERS 2005; 95:087204. [PMID: 16196897 DOI: 10.1103/physrevlett.95.087204] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2005] [Indexed: 05/04/2023]
Abstract
Magnetic susceptibility and heat capacity measurements as a function of temperature on a single-crystal sample of a spin-ladder material, Na2Co2(C2O4)3(H2O)2, are reported. Principal susceptibilities, parallel and perpendicular to the ladder direction, respectively, show broad maxima around 22 and 17 K. Both susceptibilities decay exponentially down to about 5 K and thereafter they are essentially independent of temperature. These findings amount to a signature of a quantum phase transition from a spin-liquid to Néel ordered state previously predicted theoretically. No anomaly is found in the heat capacity around the transition temperature.
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Affiliation(s)
- Z Honda
- Faculty of Engineering, Saitama University, Urawa, Saitama 338-8570, Japan
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46
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Capriotti L, Sachdev S. Low-temperature broken-symmetry phases of spiral antiferromagnets. PHYSICAL REVIEW LETTERS 2004; 93:257206. [PMID: 15697936 DOI: 10.1103/physrevlett.93.257206] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Indexed: 05/24/2023]
Abstract
We study Heisenberg antiferromagnets with nearest- (J1) and third- (J3) neighbor exchange on the square lattice. In the limit of spin S-->infinity, there is a zero temperature (T) Lifshitz point at J(3)=1/4J(1), with long-range spiral spin order at T=0 for J3>1/4J(1). We present classical Monte Carlo simulations and a theory for T>0 crossovers near the Lifshitz point: spin rotation symmetry is restored at any T>0, but there is a broken lattice reflection symmetry for 0< or =T<T(c) approximately (J3-1/4J(1))S2. The transition at T=T(c) is consistent with Ising universality. We also discuss the quantum phase diagram for finite S.
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Affiliation(s)
- Luca Capriotti
- Valuation Risk Group, Credit Suisse First Boston (Europe) Ltd., One Cabot Square, London E14 4QJ, UK
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47
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Jack RL, Lee DKK, Cooper NR. Dissipation and tunneling in quantum Hall bilayers. PHYSICAL REVIEW LETTERS 2004; 93:126803. [PMID: 15447297 DOI: 10.1103/physrevlett.93.126803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2004] [Indexed: 05/24/2023]
Abstract
We discuss the interplay between transport and intrinsic dissipation in quantum Hall bilayers, within the framework of a simple thought experiment. We compute, for the first time, quantum corrections to the semiclassical dynamics of this system. This allows us to reinterpret tunneling measurements on these systems. We find a strong peak in the zero-temperature tunneling current that arises from the decay of Josephson-like oscillations into incoherent charge fluctuations. In the presence of an in-plane field, resonances in the tunneling current develop an asymmetric line shape.
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Affiliation(s)
- Robert L Jack
- Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, United Kingdom
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48
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Senthil T, Vishwanath A, Balents L, Sachdev S, Fisher MPA. Deconfined Quantum Critical Points. Science 2004; 303:1490-4. [PMID: 15001771 DOI: 10.1126/science.1091806] [Citation(s) in RCA: 218] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The theory of second-order phase transitions is one of the foundations of modern statistical mechanics and condensed-matter theory. A central concept is the observable order parameter, whose nonzero average value characterizes one or more phases. At large distances and long times, fluctuations of the order parameter(s) are described by a continuum field theory, and these dominate the physics near such phase transitions. We show that near second-order quantum phase transitions, subtle quantum interference effects can invalidate this paradigm, and we present a theory of quantum critical points in a variety of experimentally relevant two-dimensional antiferromagnets. The critical points separate phases characterized by conventional "confining" order parameters. Nevertheless, the critical theory contains an emergent gauge field and "deconfined" degrees of freedom associated with fractionalization of the order parameters. We propose that this paradigm for quantum criticality may be the key to resolving a number of experimental puzzles in correlated electron systems and offer a new perspective on the properties of complex materials.
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Affiliation(s)
- T Senthil
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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49
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Zwerger W. Anomalous fluctuations in phases with a broken continuous symmetry. PHYSICAL REVIEW LETTERS 2004; 92:027203. [PMID: 14753966 DOI: 10.1103/physrevlett.92.027203] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2003] [Indexed: 05/24/2023]
Abstract
It is shown that the Goldstone modes associated with a broken continuous symmetry lead to anomalously large fluctuations of the zero field order parameter at any temperature below T(c). In dimensions 2<d<4, the variance of the extensive spontaneous magnetization scales as L4 with the system size L, independent of the order parameter dynamics. The anomalous scaling is a consequence of the 1/q(4-d) divergence of the longitudinal susceptibility. For ground states in two dimensions with Goldstone modes vanishing linearly with momentum, the dynamical susceptibility contains a singular contribution (q(2)-omega(2)/c(2))(-1/2). The dynamic structure factor thus exhibits a critical continuum above the undamped spin wave pole, which may be detected by neutron scattering in the Néel phase of 2D quantum antiferromagnets.
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Affiliation(s)
- W Zwerger
- Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Austria
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50
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Sandvik AW. Multicritical point in a diluted bilayer Heisenberg quantum antiferromagnet. PHYSICAL REVIEW LETTERS 2002; 89:177201. [PMID: 12398701 DOI: 10.1103/physrevlett.89.177201] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2002] [Indexed: 05/24/2023]
Abstract
The S=1/2 Heisenberg bilayer antiferromagnet with randomly removed interlayer dimers is studied using quantum Monte Carlo simulations. A zero-temperature multicritical point (p(*),g(*)) at the classical percolation density p=p(*) and interlayer coupling g(*) approximately equal 0.16 is demonstrated. The quantum critical exponents of the percolating cluster are determined using finite-size scaling. It is argued that the associated finite-temperature quantum critical regime extends to zero interlayer coupling and could be relevant for antiferromagnetic cuprates doped with nonmagnetic impurities.
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Affiliation(s)
- Anders W Sandvik
- Department of Physics, Abo Akademi University, Porthansgatan 3, FIN-20500 Turku, Finland
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