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Nomura Y, Sakai S, Arita R. Fermi Surface Expansion above Critical Temperature in a Hund Ferromagnet. PHYSICAL REVIEW LETTERS 2022; 128:206401. [PMID: 35657875 DOI: 10.1103/physrevlett.128.206401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 02/23/2022] [Accepted: 04/25/2022] [Indexed: 06/15/2023]
Abstract
Using a cluster extension of the dynamical mean-field theory, we show that strongly correlated metals subject to Hund's physics exhibit significant electronic structure modulations above magnetic transition temperatures. In particular, in a ferromagnet having a large local moment due to Hund's coupling (Hund's ferromagnet), the Fermi surface expands even above the Curie temperature (T_{C}) as if a spin polarization occurred. Behind this phenomenon, effective "Hund's physics" works in momentum space, originating from ferromagnetic fluctuations in the strong-coupling regime. The resulting significantly momentum-dependent (spatially nonlocal) electron correlations induce an electronic structure reconstruction involving a Fermi surface volume change and a redistribution of the momentum-space occupation. Our finding will give a deeper insight into the physics of Hund's ferromagnets above T_{C}.
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Affiliation(s)
- Yusuke Nomura
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Shiro Sakai
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Ryotaro Arita
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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Fabrizio M. Emergent quasiparticles at Luttinger surfaces. Nat Commun 2022; 13:1561. [PMID: 35322010 PMCID: PMC8943186 DOI: 10.1038/s41467-022-29190-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 02/11/2022] [Indexed: 12/01/2022] Open
Abstract
In periodic systems of interacting electrons, Fermi and Luttinger surfaces refer to the locations within the Brillouin zone of poles and zeros, respectively, of the single-particle Green’s function at zero energy and temperature. Such difference in analytic properties underlies the emergence of well-defined quasiparticles close to a Fermi surface, in contrast to their supposed non-existence close to a Luttinger surface, where the single-particle density-of-states vanishes at zero energy. We here show that, contrary to such common belief, dispersive ‘quasiparticles’ with infinite lifetime do exist also close to a pseudo-gapped Luttinger surface. Thermodynamic and dynamic properties of such ‘quasiparticles’ are just those of conventional ones. For instance, they yield well-defined quantum oscillations in Luttinger surface and linear-in-temperature specific heat, which is striking given the vanishing density of states of physical electrons, but actually not uncommon in strongly correlated materials. The analytic properties of Fermi surfaces give rise to quasiparticles. Now, it is shown that similarly, quasiparticles can be associated with Luttinger surfaces - the locations in the Brillouin zone of zeros of the single-particle Green’s function at zero energy and temperature.
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Affiliation(s)
- Michele Fabrizio
- International School for Advanced Studies (SISSA), Via Bonomea 265, 34136, Trieste, Italy.
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Li L, Lee CH. Non-Hermitian Pseudo-Gaps. Sci Bull (Beijing) 2022; 67:685-690. [DOI: 10.1016/j.scib.2022.01.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 12/06/2021] [Accepted: 12/28/2021] [Indexed: 11/24/2022]
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Nagai Y, Qi Y, Isobe H, Kozii V, Fu L. DMFT Reveals the Non-Hermitian Topology and Fermi Arcs in Heavy-Fermion Systems. PHYSICAL REVIEW LETTERS 2020; 125:227204. [PMID: 33315462 DOI: 10.1103/physrevlett.125.227204] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 10/23/2020] [Accepted: 10/26/2020] [Indexed: 06/12/2023]
Abstract
When a strongly correlated system supports well-defined quasiparticles, it allows for an elegant one-body effective description within the non-Hermitian topological theory. While the microscopic many-body Hamiltonian of a closed system remains Hermitian, the one-body quasiparticle Hamiltonian is non-Hermitian due to the finite quasiparticle lifetime. We use such a non-Hermitian description in the heavy-fermion two-dimensional systems with the momentum-dependent hybridization to reveal a fascinating phenomenon which can be directly probed by the spectroscopic measurements, the bulk "Fermi arcs." Starting from a simple two-band model, we first combine the phenomenological approach with the perturbation theory to show the existence of the Fermi arcs and reveal their connection to the topological exceptional points, special points in the Brillouin zone where the Hamiltonian is nondiagonalizable. The appearance of such points necessarily requires that the electrons belonging to different orbitals have different lifetimes. This requirement is naturally satisfied in the heavy-fermion systems, where the itinerant c electrons experience much weaker interaction than the localized f electrons. We then utilize the dynamical mean field theory to numerically calculate the spectral function and confirm our findings. We show that the concept of the exceptional points in the non-Hermitian quasiparticle Hamiltonians is a powerful tool for predicting new phenomena in strongly correlated electron systems.
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Affiliation(s)
- Yuki Nagai
- CCSE, Japan Atomic Energy Agency, 178-4-4, Wakashiba, Kashiwa, Chiba 277-0871, Japan
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Yang Qi
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Physics, Fudan University, Shanghai 200433, China
| | - Hiroki Isobe
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Vladyslav Kozii
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Kohno M. Characteristics of the Mott transition and electronic states of high-temperature cuprate superconductors from the perspective of the Hubbard model. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2018; 81:042501. [PMID: 29300706 DOI: 10.1088/1361-6633/aaa53d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A fundamental issue of the Mott transition is how electrons behaving as single particles carrying spin and charge in a metal change into those exhibiting separated spin and charge excitations (low-energy spin excitation and high-energy charge excitation) in a Mott insulator. This issue has attracted considerable attention particularly in relation to high-temperature cuprate superconductors, which exhibit electronic states near the Mott transition that are difficult to explain in conventional pictures. Here, from a new viewpoint of the Mott transition based on analyses of the Hubbard model, we review anomalous features observed in high-temperature cuprate superconductors near the Mott transition.
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Affiliation(s)
- Masanori Kohno
- International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Tsukuba 305-0044, Japan
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Sakai S, Civelli M, Imada M. Hidden Fermionic Excitation Boosting High-Temperature Superconductivity in Cuprates. PHYSICAL REVIEW LETTERS 2016; 116:057003. [PMID: 26894730 DOI: 10.1103/physrevlett.116.057003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Indexed: 06/05/2023]
Abstract
The dynamics of a microscopic cuprate model, namely, the two-dimensional Hubbard model, is studied with a cluster extension of the dynamical mean-field theory. We find a nontrivial structure of the frequency-dependent self-energies, which describes an unprecedented interplay between the pseudogap and superconductivity. We show that these properties are well described by quasiparticles hybridizing with (hidden) fermionic excitations, emergent from the strong electronic correlations. The hidden fermion enhances superconductivity via a mechanism distinct from a conventional boson-mediated pairing, and originates the normal-state pseudogap. Though the hidden fermion is elusive in experiments, it can solve many experimental puzzles.
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Affiliation(s)
- Shiro Sakai
- Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656, Japan
- Center for Emergent Matter Science, RIKEN, Wako, Saitama 351-0198, Japan
| | - Marcello Civelli
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Masatoshi Imada
- Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656, Japan
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Oike H, Miyagawa K, Taniguchi H, Kanoda K. Pressure-induced Mott transition in an organic superconductor with a finite doping level. PHYSICAL REVIEW LETTERS 2015; 114:067002. [PMID: 25723239 DOI: 10.1103/physrevlett.114.067002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Indexed: 06/04/2023]
Abstract
We report the pressure study of a doped organic superconductor with a Hall coefficient and conductivity measurements. We find that maximally enhanced superconductivity and a marginal-Fermi liquid appear around a certain pressure where mobile carriers increase critically, suggesting a possible quantum phase transition between strongly and weakly correlated regimes. This observation points to the presence of a criticality in Mottness for a doped Mott insulator with tunable correlation.
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Affiliation(s)
- H Oike
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - K Miyagawa
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - H Taniguchi
- Department of Physics, Saitama University, Saitama, Saitama 338-8570, Japan
| | - K Kanoda
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
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Kohno M. Doping-induced States in the Single-particle Spectrum Originating from Magnetic Excitation of a Mott Insulator. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/j.phpro.2015.12.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Sakai S, Blanc S, Civelli M, Gallais Y, Cazayous M, Méasson MA, Wen JS, Xu ZJ, Gu GD, Sangiovanni G, Motome Y, Held K, Sacuto A, Georges A, Imada M. Raman-scattering measurements and theory of the energy-momentum spectrum for underdoped Bi2Sr2CaCuO(8+δ) superconductors: evidence of an s-wave structure for the pseudogap. PHYSICAL REVIEW LETTERS 2013; 111:107001. [PMID: 25166695 DOI: 10.1103/physrevlett.111.107001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Indexed: 06/03/2023]
Abstract
We reveal the full energy-momentum structure of the pseudogap of underdoped high-Tc cuprate superconductors. Our combined theoretical and experimental analysis explains the spectral-weight suppression observed in the B2g Raman response at finite energies in terms of a pseudogap appearing in the single-electron excitation spectra above the Fermi level in the nodal direction of momentum space. This result suggests an s-wave pseudogap (which never closes in the energy-momentum space), distinct from the d-wave superconducting gap. Recent tunneling and photoemission experiments on underdoped cuprates also find a natural explanation within the s-wave pseudogap scenario.
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Affiliation(s)
- S Sakai
- Centre de Physique Théorique, École Polytechnique, CNRS, 91128 Palaiseau, France and Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656, Japan and JST-CREST, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - S Blanc
- Laboratoire Matériaux et Phénomnes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - M Civelli
- Laboratoire de Physique des Solides, Université Paris-Sud, CNRS, UMR 8502, F-91405 Orsay Cedex, France
| | - Y Gallais
- Laboratoire Matériaux et Phénomnes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - M Cazayous
- Laboratoire Matériaux et Phénomnes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - M-A Méasson
- Laboratoire Matériaux et Phénomnes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - J S Wen
- Matter Physics and Materials Science, Brookhaven National Laboratory (BNL), Upton, New York 11973, USA
| | - Z J Xu
- Matter Physics and Materials Science, Brookhaven National Laboratory (BNL), Upton, New York 11973, USA
| | - G D Gu
- Matter Physics and Materials Science, Brookhaven National Laboratory (BNL), Upton, New York 11973, USA
| | - G Sangiovanni
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany and Institute for Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria
| | - Y Motome
- Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656, Japan
| | - K Held
- Institute for Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria
| | - A Sacuto
- Laboratoire Matériaux et Phénomnes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - A Georges
- Centre de Physique Théorique, École Polytechnique, CNRS, 91128 Palaiseau, France and JST-CREST, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan and Collège de France, 11 Place Marcelin Berthelot, 75005 Paris, France and DPMC, Université de Genève, 24 Quai Ernest Ansermet, CH-1211 Genève, Suisse
| | - M Imada
- Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656, Japan and JST-CREST, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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Kohno M. Mott transition in the two-dimensional Hubbard model. PHYSICAL REVIEW LETTERS 2012; 108:076401. [PMID: 22401230 DOI: 10.1103/physrevlett.108.076401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Indexed: 05/31/2023]
Abstract
Spectral properties of the two-dimensional Hubbard model near the Mott transition are investigated by using cluster perturbation theory. The Mott transition is characterized by freezing of the charge degrees of freedom in a single-particle excitation that leads continuously to the magnetic excitation of the Mott insulator. Various anomalous spectral features observed in cuprate high-temperature superconductors are explained in a unified manner as properties near the Mott transition.
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Affiliation(s)
- Masanori Kohno
- International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Tsukuba, Japan
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