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Márkus BG, Gmitra M, Dóra B, Csősz G, Fehér T, Szirmai P, Náfrádi B, Zólyomi V, Forró L, Fabian J, Simon F. Ultralong 100 ns spin relaxation time in graphite at room temperature. Nat Commun 2023; 14:2831. [PMID: 37198155 DOI: 10.1038/s41467-023-38288-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 04/24/2023] [Indexed: 05/19/2023] Open
Abstract
Graphite has been intensively studied, yet its electron spins dynamics remains an unresolved problem even 70 years after the first experiments. The central quantities, the longitudinal (T1) and transverse (T2) relaxation times were postulated to be equal, mirroring standard metals, but T1 has never been measured for graphite. Here, based on a detailed band structure calculation including spin-orbit coupling, we predict an unexpected behavior of the relaxation times. We find, based on saturation ESR measurements, that T1 is markedly different from T2. Spins injected with perpendicular polarization with respect to the graphene plane have an extraordinarily long lifetime of 100 ns at room temperature. This is ten times more than in the best graphene samples. The spin diffusion length across graphite planes is thus expected to be ultralong, on the scale of ~ 70 μm, suggesting that thin films of graphite - or multilayer AB graphene stacks - can be excellent platforms for spintronics applications compatible with 2D van der Waals technologies. Finally, we provide a qualitative account of the observed spin relaxation based on the anisotropic spin admixture of the Bloch states in graphite obtained from density functional theory calculations.
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Affiliation(s)
- B G Márkus
- Stavropoulos Center for Complex Quantum Matter, Department of Physics and Astronomy, University of Notre Dame, Notre Dame, IN, 46556, USA
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest, H-1525, Hungary
- Department of Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary
| | - M Gmitra
- Institute of Physics, Pavol Jozef Šafárik University in Košice, Park Angelinum 9, 040 01, Košice, Slovakia
- Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04001, Košice, Slovakia
| | - B Dóra
- Department of Theoretical Physics, Institute of Physics and MTA-BME Lendület Topology and Correlation Research Group Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary
| | - G Csősz
- Department of Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary
| | - T Fehér
- Department of Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary
| | - P Szirmai
- Laboratory of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
| | - B Náfrádi
- Laboratory of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
| | - V Zólyomi
- STFC Hartree Centre, Daresbury Laboratory, Daresbury, Warrington WA4 4AD, UK
| | - L Forró
- Stavropoulos Center for Complex Quantum Matter, Department of Physics and Astronomy, University of Notre Dame, Notre Dame, IN, 46556, USA
- Laboratory of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
| | - J Fabian
- Department of Physics, University of Regensburg, 93040, Regensburg, Germany.
| | - F Simon
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest, H-1525, Hungary.
- Department of Physics, Institute of Physics and ELKH-BME Condensed Matter Research Group Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary.
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2
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Bácsi Á, Dóra B. Kibble-Zurek scaling due to environment temperature quench in the transverse field Ising model. Sci Rep 2023; 13:4034. [PMID: 36899093 PMCID: PMC10006093 DOI: 10.1038/s41598-023-30840-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Accepted: 03/02/2023] [Indexed: 03/12/2023] Open
Abstract
The Kibble-Zurek mechanism describes defect production due to non-adiabatic passage through a critical point. Here we study its variant from ramping the environment temperature to a critical point. We find that the defect density scales as [Formula: see text] or [Formula: see text] for thermal or quantum critical points, respectively, in terms of the usual critical exponents and [Formula: see text] the speed of the drive. Both scalings describe reduced defect density compared to conventional Kibble-Zurek mechanism, which stems from the enhanced relaxation due to bath-system interaction. Ramping to the quantum critical point is investigated by studying the Lindblad equation for the transverse field Ising chain in the presence of thermalizing bath, with couplings to environment obeying detailed balance, confirming the predicted scaling. The von-Neumann or the system-bath entanglement entropy follows the same scaling. Our results are generalized to a large class of dissipative systems with power-law energy dependent bath spectral densities as well.
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Affiliation(s)
- Ádám Bácsi
- MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, Műegyetem rkp. 3., Budapest, 1111, Hungary. .,Department of Mathematics and Computational Sciences, Széchenyi István University, Győr, 9026, Hungary. .,Jožef Stefan Institute, Jamova 39, 1000, Ljubljana, Slovenia.
| | - Balázs Dóra
- MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, Műegyetem rkp. 3., Budapest, 1111, Hungary.,Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., Budapest, 1111, Hungary
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3
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Dóra B, Sticlet D, Moca CP. Correlations at PT-Symmetric Quantum Critical Point. Phys Rev Lett 2022; 128:146804. [PMID: 35476487 DOI: 10.1103/physrevlett.128.146804] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 03/07/2022] [Indexed: 06/14/2023]
Abstract
We consider a PT-symmetric Fermi gas with an exceptional point, representing the critical point between PT-symmetric and symmetry broken phases. The low energy spectrum remains linear in momentum and is identical to that of a Hermitian Fermi gas. The fermionic Green's function decays in a power law fashion for large distances, as expected from gapless excitations, although the exponent is reduced from -1 due to the quantum Zeno effect. In spite of the gapless nature of the excitations, the ground state entanglement entropy saturates to a finite value, independent of the subsystem size due to the non-Hermitian correlation length intrinsic to the system. Attractive or repulsive interaction drives the system into the PT-symmetry broken regime or opens up a gap and protects PT symmetry, respectively. Our results challenge the concept of universality in non-Hermitian systems, where quantum criticality can be masked due to non-Hermiticity.
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Affiliation(s)
- Balázs Dóra
- Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111 Budapest, Hungary
- MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111 Budapest, Hungary
| | - Doru Sticlet
- National Institute for R&D of Isotopic and Molecular Technologies, 67-103 Donat, 400293 Cluj-Napoca, Romania
| | - Cătălin Paşcu Moca
- MTA-BME Quantum Dynamics and Correlations Research Group, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111 Budapest, Hungary
- Department of Physics, University of Oradea, 410087, Oradea, Romania
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4
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Sticlet D, Dóra B, Moca CP. Kubo Formula for Non-Hermitian Systems and Tachyon Optical Conductivity. Phys Rev Lett 2022; 128:016802. [PMID: 35061493 DOI: 10.1103/physrevlett.128.016802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Revised: 08/26/2021] [Accepted: 12/02/2021] [Indexed: 06/14/2023]
Abstract
Linear response theory plays a prominent role in various fields of physics and provides us with extensive information about the thermodynamics and dynamics of quantum and classical systems. Here we develop a general theory for the linear response in non-Hermitian systems with nonunitary dynamics and derive a modified Kubo formula for the generalized susceptibility for an arbitrary (Hermitian and non-Hermitian) system and perturbation. We use this to evaluate the dynamical response of a non-Hermitian, one-dimensional Dirac model with imaginary and real masses, perturbed by a time-dependent electric field. The model has a rich phase diagram, and in particular, features a tachyon phase, where excitations travel faster than an effective speed of light. Surprisingly, we find that the dc conductivity of tachyons is finite, and the optical sum rule is exactly satisfied for all masses. Our results highlight the peculiar properties of the Kubo formula for non-Hermitian systems and are applicable for a large variety of settings.
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Affiliation(s)
- Doru Sticlet
- National Institute for R&D of Isotopic and Molecular Technologies, 67-103 Donat, 400293 Cluj-Napoca, Romania
| | - Balázs Dóra
- Department of Theoretical Physics and MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
| | - Cătălin Paşcu Moca
- MTA-BME Quantum Dynamics and Correlations Research Group, Institute of Physics, Budapest University of Technology and Economics, 1521 Budapest, Hungary
- Department of Physics, University of Oradea, 410087 Oradea, Romania
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Bácsi Á, Moca CP, Zaránd G, Dóra B. Vaporization Dynamics of a Dissipative Quantum Liquid. Phys Rev Lett 2020; 125:266803. [PMID: 33449736 DOI: 10.1103/physrevlett.125.266803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 12/07/2020] [Indexed: 06/12/2023]
Abstract
We investigate the stability of a Luttinger liquid, upon suddenly coupling it to a dissipative environment. Within the Lindblad equation, the environment couples to local currents and heats the quantum liquid up to infinite temperatures. The single particle density matrix reveals the fractionalization of fermionic excitations in the spatial correlations by retaining the initial noninteger power law exponents, accompanied by an exponential decay in time with an interaction dependent rate. The spectrum of the time evolved density matrix is gapped, which collapses gradually as -ln(t). The von Neumann entropy crosses over from the early time -tln(t) behavior to ln(t) growth for late times. The early time dynamics is captured numerically by performing simulations on spinless interacting fermions, using several numerically exact methods. Our results could be tested experimentally in bosonic Luttinger liquids.
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Affiliation(s)
- Ádám Bácsi
- MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
- Department of Mathematics and Computational Sciences, Széchenyi István University, 9026 Győr, Hungary
| | - Cătălin Paşcu Moca
- MTA-BME Quantum Dynamics and Correlations Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
- Department of Physics, University of Oradea, 410087 Oradea, Romania
| | - Gergely Zaránd
- MTA-BME Quantum Dynamics and Correlations Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
- BME-MTA Exotic Quantum Phases Research Group, Department of Theoretical Physics, Budapest University of Technology and Economics, 1521 Budapest, Hungary
| | - Balázs Dóra
- MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
- Department of Theoretical Physics, Budapest University of Technology and Economics, 1521 Budapest, Hungary
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Moca CP, Izumida W, Dóra B, Legeza Ö, Asbóth JK, Zaránd G. Topologically Protected Correlated End Spin Formation in Carbon Nanotubes. Phys Rev Lett 2020; 125:056401. [PMID: 32794861 DOI: 10.1103/physrevlett.125.056401] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 06/04/2020] [Indexed: 06/11/2023]
Abstract
For most chiralities, semiconducting nanotubes display topologically protected end states of multiple degeneracies. We demonstrate using density matrix renormalization group based quantum chemistry tools that the presence of Coulomb interactions induces the formation of robust end spins. These are the close analogs of ferromagnetic edge states emerging in graphene nanoribbons. The interaction between the two ends is sensitive to the length of the nanotube, its dielectric constant, and the size of the end spins: for S=1/2 end spins, their interaction is antiferromagnetic, while for S>1/2, it changes from antiferromagnetic to ferromagnetic as the nanotube length increases. The interaction between end spins can be controlled by changing the dielectric constant of the environment, thereby providing a possible platform for two-spin quantum manipulations.
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Affiliation(s)
- Cătălin Paşcu Moca
- MTA-BME Quantum Dynamics and Correlations Research Group, Institute of Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary
- Department of Physics, University of Oradea, 410087 Oradea, Romania
| | - Wataru Izumida
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - Balázs Dóra
- Department of Theoretical Physics and MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
| | - Örs Legeza
- Strongly Correlated Systems Lendület Research Group, Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, P.O. Box 49, H-1525 Budapest, Hungary
| | - János K Asbóth
- MTA-BME Quantum Dynamics and Correlations Research Group, Institute of Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary
- BME-MTA Exotic Quantum Phases Lendület Research Group, Institute of Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary
| | - Gergely Zaránd
- MTA-BME Quantum Dynamics and Correlations Research Group, Institute of Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary
- BME-MTA Exotic Quantum Phases Lendület Research Group, Institute of Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary
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Dóra B, Moca CP. Quantum Quench in PT-Symmetric Luttinger Liquid. Phys Rev Lett 2020; 124:136802. [PMID: 32302175 DOI: 10.1103/physrevlett.124.136802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 03/11/2020] [Indexed: 06/11/2023]
Abstract
A Luttinger liquid (LL) describes low energy excitations of many interacting one dimensional systems, and exhibits universal response both in and out of equilibrium. We analyze its behavior in the non-Hermitian realm after quantum quenching to a PT-symmetric LL by focusing on the fermionic single particle density matrix. For short times, we demonstrate the emergence of unique phenomena, characteristic to non-Hermitian systems, that correlations propagate faster than the conventional maximal speed, known as the Lieb-Robinson bound. These emergent supersonic modes travel with velocities that are multiples of the conventional light cone velocity. This behavior is argued to be generic for correlators in non-Hermitian systems. In the long time limit, we find typical LL behavior, extending the LL universality to the nonequilibrium, non-Hermitian case. Our analytical results are benchmarked numerically and indicate that the dispersal of quantum information is much faster in non-Hermitian systems.
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Affiliation(s)
- Balázs Dóra
- Department of Theoretical Physics and MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
| | - Cătălin Paşcu Moca
- MTA-BME Quantum Dynamics and Correlations Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
- Department of Physics, University of Oradea, 410087 Oradea, Romania
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8
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Bácsi Á, Moca CP, Dóra B. Dissipation-Induced Luttinger Liquid Correlations in a One-Dimensional Fermi Gas. Phys Rev Lett 2020; 124:136401. [PMID: 32302153 DOI: 10.1103/physrevlett.124.136401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Accepted: 03/09/2020] [Indexed: 06/11/2023]
Abstract
We study a one-dimensional Fermi gas in the presence of dissipative coupling to environment through the Lindblad equation. The dissipation involves energy exchange with the environment and favours the relaxation of electrons to excitations. After switching on the dissipation, the system approaches a steady state, which is described by a generalized Gibbs ensemble. The fermionic single particle density matrix resembles deceivingly to that in a hermitian interaction quench. It decays inversely with the distance for short times due to the fermionic correlations in the initial state, which changes into a noninteger power law decay for late times, representing dissipation-induced Luttinger liquid behavior. However, the crossover between the two regions occurs due to dissipation-induced damping, and is unrelated to the propagation of excitations. The velocity of information spreading is set by the dissipative coupling, and differs significantly from the original sound velocity. The thermodynamic entropy grows as -t ln t initially, and saturates to an extensive value. Our results can be tested experimentally in one-dimensional Dirac systems.
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Affiliation(s)
- Ádám Bácsi
- MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
- Department of Mathematics and Computational Sciences, Széchenyi István University, 9026 Győr, Hungary
| | - Cătălin Paşcu Moca
- MTA-BME Quantum Dynamics and Correlations Research Group, Budapest University of Technology and Economics, 1521, Budapest, Hungary
- Department of Physics, University of Oradea, 410087 Oradea, Romania
- Department of Theoretical Physics, Budapest University of Technology and Economics, 1521 Budapest, Hungary
| | - Balázs Dóra
- MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
- Department of Theoretical Physics, Budapest University of Technology and Economics, 1521 Budapest, Hungary
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Moca CP, Chirla R, Dóra B, Zaránd G. Quantum Criticality and Formation of a Singular Fermi Liquid in the Attractive SU(N>2) Anderson Model. Phys Rev Lett 2019; 123:136803. [PMID: 31697511 DOI: 10.1103/physrevlett.123.136803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 08/12/2019] [Indexed: 06/10/2023]
Abstract
While much is known about repulsive quantum impurity models, significantly less attention has been devoted to their attractive counterparts. This motivated us to study the attractive SU(N) Anderson impurity model. While for the repulsive case the phase diagram features mild N dependence and the ground state is always a Fermi liquid, in the attractive case a Kosterlitz-Thouless charge localization phase transition is revealed for N>2. Beyond a critical value of attractive interaction, an abrupt jump appears in the number of particles at the impurity site, and a singular Fermi liquid state emerges, where the scattering of quasiparticles is found to exhibit power law behavior with fractional power. The capacity diverges exponentially at the quantum critical point, signaling the Kosterlitz-Thouless transition.
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Affiliation(s)
- Cătălin Paşcu Moca
- BME-MTA Exotic Quantum Phases Research Group, Institute of Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary
- Department of Physics, University of Oradea, 410087 Oradea, Romania
| | - Razvan Chirla
- Department of Physics, University of Oradea, 410087 Oradea, Romania
- School of Medicine and Pharmacy, University of Oradea, 410087 Oradea, Romania
| | - Balázs Dóra
- Department of Theoretical Physics and MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
| | - Gergely Zaránd
- BME-MTA Exotic Quantum Phases Research Group, Institute of Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary
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Dóra B, Hetényi B, Moca CP. Statistics and Dynamics of the Center-of-Mass Coordinate in a Quantum Liquid. Phys Rev Lett 2018; 121:056803. [PMID: 30118249 DOI: 10.1103/physrevlett.121.056803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Revised: 06/29/2018] [Indexed: 06/08/2023]
Abstract
Motivated by recent experiments in ultracold gases, we focus on the properties of the center-of-mass coordinate of an interacting one-dimensional Fermi gas, displaying several distinct phases. While the variance of the center of mass vanishes in insulating phases such as phase-separated and charge density wave phases, it remains finite in the metallic phase, which realizes a Luttinger liquid. By combining numerics with bosonization, we demonstrate that the autocorrelation function of the center-of-mass coordinate is universal throughout the metallic phase. It exhibits persistent oscillations, and its short time dynamics reveal important features of the quantum liquid, such as the Luttinger liquid parameter and the renormalized velocity. The full counting statistics of the center of mass follows a normal distribution already for small systems. Our results apply to nonintegrable systems as well and are within experimental reach for, e.g., carbon nanotubes and cold atomic gases.
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Affiliation(s)
- Balázs Dóra
- Department of Theoretical Physics and MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
| | - Balázs Hetényi
- Department of Theoretical Physics and BME-MTA Exotic Quantum Phases Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
| | - Cătălin Paşcu Moca
- Department of Theoretical Physics and BME-MTA Exotic Quantum Phases Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
- Department of Physics, University of Oradea, 410087 Oradea, Romania
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Heyl M, Pollmann F, Dóra B. Detecting Equilibrium and Dynamical Quantum Phase Transitions in Ising Chains via Out-of-Time-Ordered Correlators. Phys Rev Lett 2018; 121:016801. [PMID: 30028149 DOI: 10.1103/physrevlett.121.016801] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 05/04/2018] [Indexed: 06/08/2023]
Abstract
Out-of-time-ordered (OTO) correlators have developed into a central concept quantifying quantum information transport, information scrambling, and quantum chaos. In this Letter, we show that such an OTO correlator can also be used to dynamically detect equilibrium as well as nonequilibrium phase transitions in Ising chains. We study OTO correlators of an order parameter both in equilibrium and after a quantum quench for different variants of transverse-field Ising models in one dimension, including the integrable one as well as nonintegrable and long-range extensions. We find for all the studied models that the OTO correlator in ground states detects the quantum phase transition. After a quantum quench from a fully polarized state, we observe numerically for the short-range models that the asymptotic long-time value of the OTO correlator signals still the equilibrium critical points and ordered phases. For the long-range extension, the OTO correlator instead determines a dynamical quantum phase transition in the model. We discuss how our findings can be observed in current experiments of trapped ions or Rydberg atoms.
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Affiliation(s)
- Markus Heyl
- Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany
| | - Frank Pollmann
- Department of Physics, Technical University of Munich, 85748 Garching, Germany
| | - Balázs Dóra
- Department of Theoretical Physics and MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
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12
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Abstract
Information scrambling and the butterfly effect in chaotic quantum systems can be diagnosed by out-of-time-ordered (OTO) commutators through an exponential growth and large late time value. We show that the latter feature shows up in a strongly correlated many-body system, a Luttinger liquid, whose density fluctuations we study at long and short wavelengths, both in equilibrium and after a quantum quench. We find rich behavior combining robustly universal and nonuniversal features. The OTO commutators display temperature- and initial-state-independent behavior and grow as t^{2} for short times. For the short-wavelength density operator, they reach a sizable value after the light cone only in an interacting Luttinger liquid, where the bare excitations break up into collective modes. This challenges the common interpretation of the OTO commutator in chaotic systems. We benchmark our findings numerically on an interacting spinless fermion model in 1D and find persistence of central features even in the nonintegrable case. As a nonuniversal feature, the short-time growth exhibits a distance-dependent power.
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Affiliation(s)
- Balázs Dóra
- Department of Theoretical Physics and MTA-BME Lendület Spintronics Research Group (PROSPIN), Budapest University of Technology and Economics, 1521 Budapest, Hungary
| | - Roderich Moessner
- Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany
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13
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Dóra B, Lundgren R, Selover M, Pollmann F. Momentum-Space Entanglement and Loschmidt Echo in Luttinger Liquids after a Quantum Quench. Phys Rev Lett 2016; 117:010603. [PMID: 27419554 DOI: 10.1103/physrevlett.117.010603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Indexed: 06/06/2023]
Abstract
Luttinger liquids (LLs) arise by coupling left- and right-moving particles through interactions in one dimension. This most natural partitioning of LLs is investigated by the momentum-space entanglement after a quantum quench using analytical and numerical methods. We show that the momentum-space entanglement spectrum of a LL possesses many universal features both in equilibrium and after a quantum quench. The largest entanglement eigenvalue is identical to the Loschmidt echo, i.e., the overlap of the disentangled and final wave functions of the system. The second largest eigenvalue is the overlap of the first excited state of the disentangled system with zero total momentum and the final wave function. The entanglement gap is universal both in equilibrium and after a quantum quench. The momentum-space entanglement entropy is always extensive and saturates fast to a time independent value after the quench, in sharp contrast to a spatial bipartitioning.
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Affiliation(s)
- Balázs Dóra
- Department of Theoretical Physics and BME-MTA Exotic Quantum Phases Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
| | - Rex Lundgren
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Mark Selover
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Frank Pollmann
- Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany
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Abstract
Time-periodic perturbations due to classical electromagnetic fields are useful to engineer the topological properties of matter using the Floquet theory. Here we investigate the effect of quantized electromagnetic fields by focusing on the quantized light-matter interaction on the edge state of a quantum spin Hall insulator. A Dicke-type superradiant phase transition occurs at arbitrary weak coupling, the electronic spectrum acquires a finite gap, and the resulting ground-state manifold is topological with a Chern number of ±1. When the total number of excitations is conserved, a photocurrent is generated along the edge, being pseudoquantized as ωln(1/ω) in the low-frequency limit and decaying as 1/ω for high frequencies with ω the photon frequency. The photon spectral function exhibits a clean Goldstone mode, a Higgs-like collective mode at the optical gap and the polariton continuum.
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Affiliation(s)
- Balázs Gulácsi
- Department of Theoretical Physics and BME-MTA Exotic Quantum Phases Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
| | - Balázs Dóra
- Department of Theoretical Physics and BME-MTA Exotic Quantum Phases Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
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Abstract
The dynamic spin susceptibility (DSS) has a ubiquitous Lorentzian form around the Zeeman energy in conventional materials with weak spin orbit coupling, whose spectral width characterizes the spin relaxation rate. We show that DSS has an unusual non-Lorentzian form in topological insulators, which are characterized by strong SOC, and the anisotropy of the DSS reveals the orientation of the underlying spin texture of topological states. At zero temperature, the high frequency part of DSS is universal and increases in certain directions as ωd−1 with d = 2 and 3 for surface states and Weyl semimetals, respectively, while for helical edge states, the interactions renormalize the exponent as d = 2K − 1 with K the Luttinger-liquid parameter. As a result, spin relaxation rate cannot be deduced from the DSS in contrast to the case of usual metals, which follows from the strongly entangled spin and charge degrees of freedom in these systems.
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Affiliation(s)
- Balázs Dóra
- BME-MTA Exotic Quantum Phases Research Group, Budapest University of Technology and Economics, PoBox 91, H-1521 Budapest, Hungary.,Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendulet Spintronics Research Group (PROSPIN), PoBox 91, H-1521 Budapest, Hungary
| | - Ferenc Simon
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendulet Spintronics Research Group (PROSPIN), PoBox 91, H-1521 Budapest, Hungary
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16
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Dóra B, Pollmann F. Absence of Orthogonality Catastrophe after a Spatially Inhomogeneous Interaction Quench in Luttinger Liquids. Phys Rev Lett 2015; 115:096403. [PMID: 26371667 DOI: 10.1103/physrevlett.115.096403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Indexed: 06/05/2023]
Abstract
We investigate the Loschmidt echo, the overlap of the initial and final wave functions of Luttinger liquids after a spatially inhomogeneous interaction quench. In studying the Luttinger model, we obtain an analytic solution of the bosonic Bogoliubov-de Gennes equations after quenching the interactions within a finite spatial region. As opposed to the power-law temporal decay following a potential quench, the interaction quench in the Luttinger model leads to a finite, hardly time-dependent overlap; therefore, no orthogonality catastrophe occurs. The steady state value of the Loschmidt echo after a sudden inhomogeneous quench is the square of the respective adiabatic overlaps. Our results are checked and validated numerically on the XXZ Heisenberg chain.
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Affiliation(s)
- Balázs Dóra
- Department of Physics and BME-MTA Exotic Quantum Phases Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary
| | - Frank Pollmann
- Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany
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17
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Abstract
Topological excitations keep fascinating physicists since many decades. While individual vortices and solitons emerge and have been observed in many areas of physics, their most intriguing higher dimensional topological relatives, skyrmions (smooth, topologically stable textures) and magnetic monopoles emerging almost necessarily in any grand unified theory and responsible for charge quantization remained mostly elusive. Here we propose that loading a three-component nematic superfluid such as 23Na into a deep optical lattice and thereby creating an insulating core, one can create topologically stable skyrmion textures. The skyrmion's extreme stability and its compact geometry enable one to investigate the skyrmion's structure, and the interplay of topology and excitations in detail. In particular, the superfluid's excitation spectrum as well as the quantum numbers are demonstrated to change dramatically due to the skyrmion, and reflect the presence of a trapped monopole, as imposed by the skyrmion's topology.
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Affiliation(s)
- M Kanász-Nagy
- 1] BME-MTA Exotic Quantum Phases Research Group, Budapest University of Technology and Economics and MTA-BME Condensed Matter Research Group, Budapest 1521, Hungary [2] Department of Physics, Harvard University, Cambridge, MA 02138, U.S.A
| | - B Dóra
- 1] BME-MTA Exotic Quantum Phases Research Group, Budapest University of Technology and Economics and MTA-BME Condensed Matter Research Group, Budapest 1521, Hungary [2] Department of Physics, Budapest University of Technology and Economics and MTA-BME Condensed Matter Research Group, Budapest 1521, Hungary
| | - E A Demler
- Department of Physics, Harvard University, Cambridge, MA 02138, U.S.A
| | - G Zaránd
- BME-MTA Exotic Quantum Phases Research Group, Budapest University of Technology and Economics and MTA-BME Condensed Matter Research Group, Budapest 1521, Hungary
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18
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Boross P, Dóra B, Kiss A, Simon F. A unified theory of spin-relaxation due to spin-orbit coupling in metals and semiconductors. Sci Rep 2013; 3:3233. [PMID: 24252975 PMCID: PMC3834866 DOI: 10.1038/srep03233] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 10/30/2013] [Indexed: 11/09/2022] Open
Abstract
Spintronics is an emerging paradigm with the aim to replace conventional electronics by using electron spins as information carriers. Its utility relies on the magnitude of the spin-relaxation, which is dominated by spin-orbit coupling (SOC). Yet, SOC induced spin-relaxation in metals and semiconductors is discussed for the seemingly orthogonal cases when inversion symmetry is retained or broken by the so-called Elliott-Yafet and D'yakonov-Perel' spin-relaxation mechanisms, respectively. We unify the two theories on general grounds for a generic two-band system containing intra- and inter-band SOC. While the previously known limiting cases are recovered, we also identify parameter domains when a crossover occurs between them, i.e. when an inversion symmetry broken state evolves from a D'yakonov-Perel' to an Elliott-Yafet type of spin-relaxation and conversely for a state with inversional symmetry. This provides an ultimate link between the two mechanisms of spin-relaxation.
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Affiliation(s)
- Péter Boross
- 1] Department of Physics, Budapest University of Technology and Economics, Budapest, Hungary [2] Department of Materials Physics, Eötvös University, Budapest, Hungary
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19
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Dóra B, Pollmann F, Fortágh J, Zaránd G. Loschmidt echo and the many-body orthogonality catastrophe in a qubit-coupled Luttinger liquid. Phys Rev Lett 2013; 111:046402. [PMID: 23931387 DOI: 10.1103/physrevlett.111.046402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Indexed: 06/02/2023]
Abstract
We investigate the many-body generalization of the orthogonality catastrophe by studying the generalized Loschmidt echo of Luttinger liquids (LLs) after a global change of interaction. It decays exponentially with system size and exhibits universal behavior: the steady state exponent after quenching back and forth n times between 2 LLs (bang-bang protocol) is 2n times bigger than that of the adiabatic overlap and depends only on the initial and final LL parameters. These are corroborated numerically by matrix-product state based methods of the XXZ Heisenberg model. An experimental setup consisting of a hybrid system containing cold atoms and a flux qubit coupled to a Feshbach resonance is proposed to measure the Loschmidt echo using rf spectroscopy or Ramsey interferometry.
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Affiliation(s)
- Balázs Dóra
- BME-MTA Exotic Quantum Phases Research Group, Budapest University of Technology and Economics, Budapest 1521, Hungary.
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20
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Demkó L, Bordács S, Vojta T, Nozadze D, Hrahsheh F, Svoboda C, Dóra B, Yamada H, Kawasaki M, Tokura Y, Kézsmárki I. Disorder promotes ferromagnetism: rounding of the quantum phase transition in Sr(1-x)Ca(x)RuO3. Phys Rev Lett 2012; 108:185701. [PMID: 22681090 DOI: 10.1103/physrevlett.108.185701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Indexed: 06/01/2023]
Abstract
The subtle interplay of randomness and quantum fluctuations at low temperatures gives rise to a plethora of unconventional phenomena in systems ranging from quantum magnets and correlated electron materials to ultracold atomic gases. Particularly strong disorder effects have been predicted to occur at zero-temperature quantum phase transitions. Here, we demonstrate that the composition-driven ferromagnetic-to-paramagnetic quantum phase transition in Sr(1-x)Ca(x)RuO3 is completely destroyed by the disorder introduced via the different ionic radii of the randomly distributed Sr and Ca ions. Using a magneto-optical technique, we map the magnetic phase diagram in the composition-temperature space. We find that the ferromagnetic phase is significantly extended by the disorder and develops a pronounced tail over a broad range of the composition x. These findings are explained by a microscopic model of smeared quantum phase transitions in itinerant magnets. Moreover, our theoretical study implies that correlated disorder is even more powerful in promoting ferromagnetism than random disorder.
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Affiliation(s)
- L Demkó
- Department of Physics, Budapest University of Technology and Economics and Condensed Matter Research Group of the Hungarian Academy of Sciences, 1111 Budapest, Hungary
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21
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Dóra B, Cayssol J, Simon F, Moessner R. Optically engineering the topological properties of a spin Hall insulator. Phys Rev Lett 2012; 108:056602. [PMID: 22400947 DOI: 10.1103/physrevlett.108.056602] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Indexed: 05/31/2023]
Abstract
Time-periodic perturbations can be used to engineer topological properties of matter by altering the Floquet band structure. This is demonstrated for the helical edge state of a spin Hall insulator in the presence of monochromatic circularly polarized light. The inherent spin structure of the edge state is influenced by the Zeeman coupling and not by the orbital effect. The photocurrent (and the magnetization along the edge) develops a finite, helicity-dependent expectation value and turns from dissipationless to dissipative with increasing radiation frequency, signalling a change in the topological properties. The connection with Thouless' charge pumping and nonequilibrium zitterbewegung is discussed, together with possible experiments.
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Affiliation(s)
- Balázs Dóra
- Department of Physics, Budapest University of Technology and Economics, Budafoki út 8, 1111 Budapest, Hungary.
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22
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Kiss A, Pályi A, Ihara Y, Wzietek P, Simon P, Alloul H, Zólyomi V, Koltai J, Kürti J, Dóra B, Simon F. Enhanced NMR relaxation of Tomonaga-Luttinger liquids and the magnitude of the carbon hyperfine coupling in single-wall carbon nanotubes. Phys Rev Lett 2011; 107:187204. [PMID: 22107670 DOI: 10.1103/physrevlett.107.187204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Indexed: 05/31/2023]
Abstract
Recent transport measurements [Churchill et al. Nature Phys. 5, 321 (2009)] found a surprisingly large, 2-3 orders of magnitude larger than usual (13)C hyperfine coupling (HFC) in (13)C enriched single-wall carbon nanotubes. We formulate the theory of the nuclear relaxation time in the framework of the Tomonaga-Luttinger liquid theory to enable the determination of the HFC from recent data by Ihara et al. [Europhys. Lett. 90, 17,004 (2010)]. Though we find that 1/T(1) is orders of magnitude enhanced with respect to a Fermi-liquid behavior, the HFC has its usual, small value. Then, we reexamine the theoretical description used to extract the HFC from transport experiments and show that similar features could be obtained with HFC-independent system parameters.
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Affiliation(s)
- A Kiss
- Budapest University of Technology and Economics, Institute of Physics and Condensed Matter Research Group of the Hungarian Academy of Sciences, H-1521 Budapest, Hungary
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23
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Dóra B, Haque M, Zaránd G. Crossover from adiabatic to sudden interaction quench in a Luttinger liquid. Phys Rev Lett 2011; 106:156406. [PMID: 21568587 DOI: 10.1103/physrevlett.106.156406] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Indexed: 05/30/2023]
Abstract
Motivated by recent experiments on interacting cold atoms, we analyze interaction quenches in Luttinger liquids (LLs), where the interaction is ramped from zero to a finite value within a finite time. The fermionic single particle density matrix reveals several regions of spatial and temporal coordinates relative to the quench time, termed as Fermi liquid, sudden quench LL, adiabatic LL regime, and a LL regime with a time-dependent exponent. The various regimes can also be observed in the momentum distribution of the fermions, directly accessible through time of flight experiments. Most of our results apply to arbitrary quench protocols.
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Affiliation(s)
- Balázs Dóra
- Department of Physics, Budapest University of Technology and Economics, Budafoki út 8, 1111 Budapest, Hungary.
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24
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Nakamura M, Castro EV, Dóra B. Valley symmetry breaking in bilayer graphene: a test of the minimal model. Phys Rev Lett 2009; 103:266804. [PMID: 20366331 DOI: 10.1103/physrevlett.103.266804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Indexed: 05/29/2023]
Abstract
Physical properties reflecting the valley asymmetry of Landau levels in a biased bilayer graphene under a magnetic field are discussed. Within the 4-band continuum model with a Hartree-corrected self-consistent gap and finite damping factor we predict the appearance of anomalous steps in quantized Hall conductivity due to the degeneracy lifting of Landau levels. Moreover, the valley symmetry breaking effect appears as a nonsemiclassical de Haas-van Alphen effect where the reduction of the oscillation period to half cannot be accounted for through quasiclassical quantization of the orbits in reciprocal space.
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Affiliation(s)
- Masaaki Nakamura
- Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan
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25
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Abstract
A theory of nuclear magnetic resonance (NMR) in graphene is presented. The canonical form of the electron-nucleus hyperfine interaction is strongly modified by the linear electronic dispersion. The NMR shift and spin-lattice relaxation time are calculated as a function of temperature, chemical potential, and magnetic field, and three distinct regimes are identified: Fermi-, Dirac-gas, and extreme quantum limit behaviors. A critical spectrometer assessment shows that NMR is within reach for fully 13C enriched graphene of reasonable size.
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Affiliation(s)
- Balázs Dóra
- Max-Planck-Institut für Physik Komplexer Systeme, Nöthnitzer Strasse 38, 01187 Dresden, Germany
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26
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Abstract
The temperature dependence of the electron-spin lifetime T1 and the g factor are anomalous in alkali fullerides (K,Rb)3C60, which cannot be explained by the canonical Elliott-Yafet theory. These materials are archetypes of strongly correlated and narrow band metals. We introduce the concept of a "complex electron-spin resonance frequency shift" to treat these measurables in a unified manner within the Kubo formalism. The theory is applicable for metals with nearly degenerate conduction bands and large momentum scattering even with an anomalous temperature dependence and sizable residual value.
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Affiliation(s)
- Balázs Dóra
- Budapest University of Technology and Economics, Institute of Physics and Condensed Matter Research Group of the Hungarian Academy of Sciences, H-1521 Budapest, Hungary.
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27
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Abstract
We investigate the relation between the canonical model of quantum optics, the Jaynes-Cummings Hamiltonian and Dirac fermions in quantizing magnetic field. We demonstrate that Rabi oscillations are observable in the optical response of graphene, providing us with a transparent picture about the structure of optical transitions. While the longitudinal conductivity reveals chaotic Rabi oscillations, the Hall component measures coherent ones. This opens up the possibility of investigating a microscopic model of a few quantum objects in a macroscopic experiment with tunable parameters.
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Affiliation(s)
- Balázs Dóra
- Max-Planck-Institut für Physik Komplexer Systeme, Nöthnitzer Strasse 38, 01187 Dresden, Germany.
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28
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Simon F, Dóra B, Murányi F, Jánossy A, Garaj S, Forró L, Bud'ko S, Petrovic C, Canfield PC. Generalized Elliott-Yafet theory of electron spin relaxation in metals: origin of the anomalous electron spin lifetime in MgB2. Phys Rev Lett 2008; 101:177003. [PMID: 18999776 DOI: 10.1103/physrevlett.101.177003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Indexed: 05/27/2023]
Abstract
The temperature dependence of the electron-spin relaxation time in MgB2 is anomalous as it does not follow the resistivity above 150 K; it has a maximum around 400 K and decreases for higher temperatures. This violates the well established Elliot-Yafet theory of spin relaxation in metals. The anomaly occurs when the quasiparticle scattering rate (in energy units) is comparable to the energy difference between the conduction and a neighboring bands. The anomalous behavior is related to the unique band structure of MgB2 and the large electron-phonon coupling. The saturating spin relaxation is the spin transport analogue of the Ioffe-Regel criterion of electron transport.
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Affiliation(s)
- F Simon
- Budapest University of Technology and Economics, Institute of Physics and Condensed Matter Research Group of the Hungarian Academy of Sciences, H-1521 Budapest, Hungary.
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29
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Dóra B, Gulácsi M, Koltai J, Zólyomi V, Kürti J, Simon F. Electron spin resonance signal of Luttinger liquids and single-wall carbon nanotubes. Phys Rev Lett 2008; 101:106408. [PMID: 18851238 DOI: 10.1103/physrevlett.101.106408] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Indexed: 05/26/2023]
Abstract
A comprehensive theory of electron spin resonance (ESR) for a Luttinger liquid state of correlated metals is presented. The ESR measurables such as the signal intensity and the linewidth are calculated in the framework of Luttinger liquid theory with broken spin rotational symmetry as a function of magnetic field and temperature. We obtain a significant temperature dependent homogeneous line broadening which is related to the spin-symmetry breaking and the electron-electron interaction. The result crosses over smoothly to the ESR of itinerant electrons in the noninteracting limit. These findings explain the absence of the long-sought ESR signal of itinerant electrons in single-wall carbon nanotubes when considering realistic experimental conditions.
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Affiliation(s)
- B Dóra
- Max-Planck-Institut für Physik Komplexer Systeme, Nöthnitzer Str. 38, 01187 Dresden, Germany.
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30
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Dóra B, Gulácsi M, Simon F, Kuzmany H. Spin gap and Luttinger liquid description of the NMR relaxation in carbon nanotubes. Phys Rev Lett 2007; 99:166402. [PMID: 17995273 DOI: 10.1103/physrevlett.99.166402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Indexed: 05/25/2023]
Abstract
Recent NMR experiments by Singer et al. [Singer, Phys. Rev. Lett. 95, 236403 (2005).] showed a deviation from Fermi-liquid behavior in carbon nanotubes with an energy gap evident at low temperatures. Here, a comprehensive theory for the magnetic field and temperature dependent NMR 13C spin-lattice relaxation is given in the framework of the Tomonaga-Luttinger liquid. The low temperature properties are governed by a gapped relaxation due to a spin gap ( approximately 30 K), which crosses over smoothly to the Luttinger liquid behavior with increasing temperature.
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Affiliation(s)
- Balázs Dóra
- Max-Planck-Institut für Physik Komplexer Systeme, Nöthnitzer Strasse 38, 01187 Dresden, Germany.
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31
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Mihály L, Dóra B, Ványolos A, Berger H, Forró L. Spin-lattice interaction in the quasi-one-dimensional helimagnet LiCu2O2. Phys Rev Lett 2006; 97:067206. [PMID: 17026201 DOI: 10.1103/physrevlett.97.067206] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Indexed: 05/12/2023]
Abstract
The field dependence of the electron spin resonance in a helimagnet LiCu2O2 was investigated for the first time. In the paramagnetic state, a broad resonance line was observed corresponding to a g factor of 2.3. In the critical regime, around the paramagnetic to helimagnetic phase transition the resonance broadens and shifts to higher frequencies. A narrow signal is recovered at a low temperature, corresponding to a spin gap of 1.4 meV in zero field. A comprehensive model of the magnons is presented, using exchange parameters from neutron scattering [T. Masuda Phys. Rev. B 72, 014405 (2005)10.1103/PhysRevB.72.014405] and the spin anisotropy determined here. The role of the quantum fluctuations is discussed.
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Affiliation(s)
- László Mihály
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, USA
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32
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Maki K, Dóra B, Kartsovnik M, Virosztek A, Korin-Hamzić B, Basletić M. Unconventional charge-density wave in the organic conductor alpha-(BEDT-TTF)2KHg(SCN)4. Phys Rev Lett 2003; 90:256402. [PMID: 12857150 DOI: 10.1103/physrevlett.90.256402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2002] [Indexed: 05/24/2023]
Abstract
The low temperature phase (LTP) of alpha-(BEDT-TTF)2KHg(SCN)(4) salt is known for its surprising angular dependent magnetoresistance (ADMR), which has been studied intensively in the last decade. However, the nature of the LTP has not been understood until now. Here we analyze theoretically ADMR in unconventional (or nodal) charge-density wave (UCDW). In magnetic field the quasiparticle spectrum in UCDW is quantized, which gives rise to spectacular ADMR. The present model accounts for many striking features of ADMR data in alpha-(BEDT-TTF)2KHg(SCN)(4).
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Affiliation(s)
- Kazumi Maki
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089-0484, USA
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