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Ning H, Mehio O, Buchhold M, Kurumaji T, Refael G, Checkelsky JG, Hsieh D. Signatures of Ultrafast Reversal of Excitonic Order in Ta_{2}NiSe_{5}. Phys Rev Lett 2020; 125:267602. [PMID: 33449742 DOI: 10.1103/physrevlett.125.267602] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 08/25/2020] [Accepted: 11/24/2020] [Indexed: 06/12/2023]
Abstract
In the presence of electron-phonon coupling, an excitonic insulator harbors two degenerate ground states described by an Ising-type order parameter. Starting from a microscopic Hamiltonian, we derive the equations of motion for the Ising order parameter in the phonon coupled excitonic insulator Ta_{2}NiSe_{5} and show that it can be controllably reversed on ultrashort timescales using appropriate laser pulse sequences. Using a combination of theory and time-resolved optical reflectivity measurements, we report evidence of such order parameter reversal in Ta_{2}NiSe_{5} based on the anomalous behavior of its coherently excited order-parameter-coupled phonons. Our Letter expands the field of ultrafast order parameter control beyond spin and charge ordered materials.
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Affiliation(s)
- H Ning
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
| | - O Mehio
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
| | - M Buchhold
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
| | - T Kurumaji
- Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - G Refael
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
| | - J G Checkelsky
- Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - D Hsieh
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
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2
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Ron A, Chaudhary S, Zhang G, Ning H, Zoghlin E, Wilson SD, Averitt RD, Refael G, Hsieh D. Ultrafast Enhancement of Ferromagnetic Spin Exchange Induced by Ligand-to-Metal Charge Transfer. Phys Rev Lett 2020; 125:197203. [PMID: 33216570 DOI: 10.1103/physrevlett.125.197203] [Citation(s) in RCA: 2] [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: 12/10/2019] [Revised: 08/17/2020] [Accepted: 10/02/2020] [Indexed: 06/11/2023]
Abstract
We theoretically predict and experimentally demonstrate a nonthermal pathway to optically enhance superexchange interaction energies in a material based on exciting ligand-to-metal charge-transfer transitions, which introduces lower-order virtual hopping contributions that are absent in the ground state. We demonstrate this effect in the layered ferromagnetic insulator CrSiTe_{3} by exciting Te-to-Cr charge-transfer transitions using ultrashort laser pulses and detecting coherent phonon oscillations that are impulsively generated by superexchange enhancement via magneto-elastic coupling. This mechanism kicks in below the temperature scale where short-range in-plane spin correlations begin to develop and disappears when the excitation energy is tuned away from the charge-transfer resonance, consistent with our predictions.
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Affiliation(s)
- A Ron
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel Aviv, 69978, Israel
| | - S Chaudhary
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
| | - G Zhang
- Department of Physics, University of California, San Diego, La Jolla, California 92093, USA
| | - H Ning
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
| | - E Zoghlin
- Materials Department, University of California, Santa Barbara, Santa Barbara, California 93106, USA
| | - S D Wilson
- Materials Department, University of California, Santa Barbara, Santa Barbara, California 93106, USA
| | - R D Averitt
- Department of Physics, University of California, San Diego, La Jolla, California 92093, USA
| | - G Refael
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
| | - D Hsieh
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
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Abstract
We show that disorder, when sufficiently strong, can transform an ordinary metal with strong spin-orbit coupling into a strong topological "Anderson" insulator, a new topological phase of quantum matter in three dimensions characterized by disordered insulating bulk and topologically protected conducting surface states.
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Affiliation(s)
- H-M Guo
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada V6T 1Z1
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Lee TE, Tam H, Refael G, Rogers JL, Cross MC. Vortices and the entrainment transition in the two-dimensional Kuramoto model. Phys Rev E Stat Nonlin Soft Matter Phys 2010; 82:036202. [PMID: 21230156 DOI: 10.1103/physreve.82.036202] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Indexed: 05/30/2023]
Abstract
We study synchronization in the two-dimensional lattice of coupled phase oscillators with random intrinsic frequencies. When the coupling K is larger than a threshold K{E} , there is a macroscopic cluster of frequency-synchronized oscillators. We explain why the macroscopic cluster disappears at K{E} . We view the system in terms of vortices, since cluster boundaries are delineated by the motion of these topological defects. In the entrained phase (K>K{E}) , vortices move in fixed paths around clusters, while in the unentrained phase (K<K{E}) , vortices sometimes wander off. These deviant vortices are responsible for the disappearance of the macroscopic cluster. The regularity of vortex motion is determined by whether clusters behave as single effective oscillators. The unentrained phase is also characterized by time-dependent cluster structure and the presence of chaos. Thus, the entrainment transition is actually an order-chaos transition. We present an analytical argument for the scaling K{E}∼K{L} for small lattices, where K{L} is the threshold for phase locking. By also deriving the scaling K{L}∼log N , we thus show that K{E}∼log N for small N , in agreement with numerics. In addition, we show how to use the linearized model to predict where vortices are generated.
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Affiliation(s)
- Tony E Lee
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
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Alicea J, Motrunich OI, Refael G, Fisher MPA. Interlayer coherent composite Fermi liquid phase in quantum Hall bilayers. Phys Rev Lett 2009; 103:256403. [PMID: 20366269 DOI: 10.1103/physrevlett.103.256403] [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: 08/26/2009] [Indexed: 05/29/2023]
Abstract
We introduce an interlayer coherent composite Fermi liquid for nu = 1/2 + 1/2 bilayers, in which interlayer Coulomb repulsion drives exciton condensation of composite fermions. As a result, composite fermions propagate coherently between layers--even though electrons do not--and form bonding and antibonding Fermi seas. This phase is compressible with respect to symmetric currents but quantum Hall-like in the counterflow channel. Quantum oscillations of the composite Fermi seas generate a new series of incompressible states at nu = p/[2(p +/- 1)] per layer (p an integer), which is a bilayer analogue of Jain's sequence.
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Affiliation(s)
- Jason Alicea
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
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Lee TE, Refael G, Cross MC, Kogan O, Rogers JL. Universality in the one-dimensional chain of phase-coupled oscillators. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 80:046210. [PMID: 19905418 DOI: 10.1103/physreve.80.046210] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2009] [Indexed: 05/28/2023]
Abstract
We apply a recently developed renormalization-group (RG) method to study synchronization in a one-dimensional chain of phase-coupled oscillators in the regime of weak randomness. The RG predicts how oscillators with randomly distributed frequencies and couplings form frequency-synchronized clusters. Although the RG was originally intended for strong randomness, i.e., for distributions with long tails, we find good agreement with numerical simulations even in the regime of weak randomness. We use the RG flow to derive how the correlation length scales with the width of the coupling distribution in the limit of large coupling. This leads to the identification of a universality class of distributions with the same critical exponent nu . We also find universal scaling for small coupling. Finally, we show that the RG flow is characterized by a universal approach to the unsynchronized fixed point, which provides physical insight into low-frequency clusters.
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Affiliation(s)
- Tony E Lee
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
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Kogan O, Rogers JL, Cross MC, Refael G. Renormalization group approach to oscillator synchronization. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 80:036206. [PMID: 19905199 DOI: 10.1103/physreve.80.036206] [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] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Indexed: 05/28/2023]
Abstract
We develop a renormalization group method to investigate synchronization clusters in a one-dimensional chain of nearest-neighbor coupled phase oscillators. The method is best suited for chains with strong disorder in the intrinsic frequencies and coupling strengths. The results are compared with numerical simulations of the chain dynamics and good agreement in several characteristics is found. We apply the renormalization group and simulations to Lorentzian distributions of intrinsic frequencies and couplings and investigate the statistics of the resultant cluster sizes and frequencies, as well as the dependence of the characteristic cluster length upon parameters of these Lorentzian distributions.
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Affiliation(s)
- Oleg Kogan
- Department of Materials Science, California Institute of Technology, 1200 E California Boulevard, Pasadena, California 91125, USA
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Gurarie V, Refael G, Chalker JT. Excitations of one-dimensional Bose-Einstein condensates in a random potential. Phys Rev Lett 2008; 101:170407. [PMID: 18999729 DOI: 10.1103/physrevlett.101.170407] [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: 06/30/2008] [Indexed: 05/27/2023]
Abstract
We examine bosons hopping on a one-dimensional lattice in the presence of a random potential at zero temperature. Bogoliubov excitations of the Bose-Einstein condensate formed under such conditions are localized, with the localization length diverging at low frequency as l(omega) approximately 1/omega(alpha). We show that the well-known result alpha=2 applies only for sufficiently weak random potential. As the random potential is increased beyond a certain strength, alpha starts decreasing. At a critical strength of the potential, when the system of bosons is at the transition from a superfluid to an insulator, alpha=1. This result is relevant for understanding the behavior of the atomic Bose-Einstein condensates in the presence of random potential, and of the disordered Josephson junction arrays.
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Affiliation(s)
- V Gurarie
- Department of Physics, University of Colorado, Boulder, CO 80309, USA
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Klich I, Lannert C, Refael G. Supercurrent survival under a Rosen-Zener quench of hard-core bosons. Phys Rev Lett 2007; 99:205303. [PMID: 18233155 DOI: 10.1103/physrevlett.99.205303] [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: 06/29/2007] [Indexed: 05/25/2023]
Abstract
We study the survival of supercurrents in a system of impenetrable bosons on a lattice, subject to a quantum quench from its critical superfluid phase to an insulating phase. We show that the evolution of the current when the quench follows a Rosen-Zener profile is exactly solvable. This allows us to analyze a quench of arbitrary rate, from a sudden destruction of the superfluid to a slow opening of a gap. The decay and oscillations of the current are analytically derived and studied numerically along with the momentum distribution after the quench. In the case of small supercurrent boosts nu, we find that the current surviving at long times is proportional to nu3.
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Affiliation(s)
- I Klich
- Department of Physics, California Institute of Technology, MC 114-36 Pasadena, California 91125, USA
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Abstract
We study the interplay between superfluidity and magnetism in a multicomponent gas of ultracold fermions. Ward-Takahashi identities constrain possible mean-field states describing order parameters for both pairing and magnetization. The structure of global phase diagrams arises from competition among these states as functions of anisotropies in chemical potential, density, or interactions. They exhibit first and second order phase transition as well as multicritical points, metastability regions, and phase separation. We comment on experimental signatures in ultracold atoms.
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Affiliation(s)
- R W Cherng
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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Galitski VM, Refael G, Fisher MPA, Senthil T. Vortices and quasiparticles near the superconductor-insulator transition in thin films. Phys Rev Lett 2005; 95:077002. [PMID: 16196816 DOI: 10.1103/physrevlett.95.077002] [Citation(s) in RCA: 19] [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: 05/09/2005] [Indexed: 05/04/2023]
Abstract
We study the low temperature behavior of an amorphous superconducting film driven normal by a perpendicular magnetic-field (B). For this purpose we introduce a new two-fluid formulation consisting of fermionized field-induced vortices and electrically neutralized Bogoliubov quasiparticles (spinons) interacting via a long-ranged statistical interaction. This approach allows us to access a novel non-Fermi-liquid phase, which naturally interpolates between the low B superconductor and the high B normal metal. We discuss the properties of the resulting "vortex metal" phase.
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Affiliation(s)
- Victor M Galitski
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, 93106-4030, USA
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12
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Abstract
For quantum critical spin chains without disorder, it is known that the entanglement of a segment of N>>1 spins with the remainder is logarithmic in N with a prefactor fixed by the central charge of the associated conformal field theory. We show that for a class of strongly random quantum spin chains, the same logarithmic scaling holds for mean entanglement at criticality and defines a critical entropy equivalent to central charge in the pure case. This effective central charge is obtained for Heisenberg, XX, and quantum Ising chains using an analytic real-space renormalization-group approach believed to be asymptotically exact. For these random chains, the effective universal central charge is characteristic of a universality class and is consistent with a c-theorem.
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Affiliation(s)
- G Refael
- Kavli Institute of Theoretical Physics, Santa Barbara, California 93106, USA
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Hussein O, Rosenblat M, Refael G, Aviram M. Dietary selenium increases cellular glutathione peroxidase activity and reduces the enhanced susceptibility to lipid peroxidation of plasma and low-density lipoprotein in kidney transplant recipients. Transplantation 1997; 63:679-85. [PMID: 9075838 DOI: 10.1097/00007890-199703150-00012] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The glutathione system plays a major role in the protection of cells against oxidative stress in humans. The aim of the present study was to find out the relationship between the glutathione system and plasma lipid peroxidation in six renal transplant recipients (who are under oxidative stress and thus at high risk for atherosclerosis), by using dietary selenium to activate the glutathione system. 2,2'-Azobis-2-amidinopropane hydrochloride (AAPH)-induced plasma lipid peroxidation was increased (by 60%) in all six patients in comparison to normal subjects. A similar pattern of increased plasma lipid peroxidation was found even in the basal state (in the absence of added AAPH). CuSO4-induced low-density lipoprotein (LDL) oxidation measured by peroxide formation was also significantly increased by 2.3-fold in the patients' LDL in comparison to normal LDL. Even in the absence of CuSO4, the LDL oxidation state was also increased in the patients' LDL in comparison to normal LDL. We thus analyzed the effect of dietary selenium (0.2 mg/day for a period of 3 months, followed by an additional 3 months on placebo) on plasma and on LDL lipid peroxidation. Selenium treatment resulted in a 50% reduction in AAPH-induced plasma lipid peroxidation. The susceptibility of the patients' plasma to lipid peroxidation returned toward baseline values 3 months after termination of the selenium treatment. Similar results, although less pronounced (only 15% reduction), were obtained for CuSO4-induced LDL oxidation. Analyses of the patients' red blood cell (RBC) glutathione system revealed low levels of reduced glutathione and decreased activities of RBC glutathione peroxidase and glutathione reductase by 23%, 18%, and 20%, respectively, in comparison to normal RBC. Selenium treatment resulted in a significant elevation of RBC glutathione peroxidase and glutathione reductase activities and in reduced glutathione content by 64%, 57%, and 11%, respectively; this effect was also paralleled by a 39% reduction in the RBC oxidized glutathione content. On termination of the selenium treatment, and after 3 months on placebo, all of these values of the glutathione system elements returned toward baseline levels. We thus conclude that dietary selenium, which activates the glutathione system, is a potent antioxidant against plasma and LDL lipid peroxidation in renal transplant recipients, and may thus be considered antiatherogenic.
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Affiliation(s)
- O Hussein
- Department of Nephrology, Technion Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences, Haifa, Israel
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