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Xu B, Marsik P, Sheveleva E, Lyzwa F, Louat A, Brouet V, Munzar D, Bernhard C. Optical Signature of a Crossover from Mott- to Slater-Type Gap in Sr_{2}Ir_{1-x}Rh_{x}O_{4}. PHYSICAL REVIEW LETTERS 2020; 124:027402. [PMID: 32004046 DOI: 10.1103/physrevlett.124.027402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Indexed: 06/10/2023]
Abstract
With optical spectroscopy we provide evidence that the insulator-metal transition in Sr_{2}Ir_{1-x}Rh_{x}O_{4} occurs close to a crossover from the Mott- to the Slater-type. The Mott gap at x=0 persists to high temperature and evolves without an anomaly across the Néel temperature, T_{N}. Upon Rh doping, it collapses rather rapidly and vanishes around x=0.055. Notably, just as the Mott gap vanishes yet another gap appears that is of the Slater-type and develops right below T_{N}. This Slater gap is only partial and is accompanied by a reduced scattering rate of the remaining free carriers, similar as in the parent compounds of the iron arsenide superconductors.
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Affiliation(s)
- B Xu
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
| | - P Marsik
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
| | - E Sheveleva
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
| | - F Lyzwa
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
| | - A Louat
- Laboratoire de Physique des Solides, CNRS, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - V Brouet
- Laboratoire de Physique des Solides, CNRS, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - D Munzar
- Department of Condensed Matter Physics, Faculty of Science, and Central European Institute of Technology, Masaryk University, Kotlářská 2, 61137 Brno, Czech Republic
| | - C Bernhard
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
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Myasnikova AE, Nazdracheva TF, Lutsenko AV, Dmitriev AV, Dzhantemirov AH, Zhileeva EA, Moseykin DV. Strong long-range electron-phonon interaction as possible driving force for charge ordering in cuprates. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:235602. [PMID: 30840947 DOI: 10.1088/1361-648x/ab0d6c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A model resulting in charge ordering (CO) similar to that observed in cuprate superconductors is under study. It includes strong long-range electron-phonon interaction (EPI) and high density of correlated carriers. Coexistence of large bipolarons and delocalized carriers is a feature of such system. We develop generalized variation method to calculate the bipolaron size (CO period) in the ground normal state of such system at various doping. The approach allows the revealing of a possible physical reason of strongly different doping behavior of the CO wave vector in different cuprates. Obtained doping dependences of the CO period and temperature of the CO decay demonstrate quantitative agreement with those observed in cuprates. Predicted in the suggested approach ratio of the CO wave vector to the wave vector of the high-energy anomaly (HEA) in ARPES spectrum is in consent with that in cuprates. Calculated resonant x-rays scattering on the CO emerging in the model is in good agreement with experiments on cuprates including the asymmetry of the CO peaks' cross-section. A gap arises in the spectrum of delocalized carriers near antinodal direction due to their scattering on the periodic potential created by autolocalized carriers, analogously to photon crystal effect.
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Myasnikova AE, Zhileeva EA, Moseykin DV. Relaxation of strongly coupled electron and phonon fields after photoemission and high-energy part of ARPES spectra of cuprates. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:125601. [PMID: 29406313 DOI: 10.1088/1361-648x/aaad3e] [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
An approach to considering systems with a high concentration of correlated carriers and strong long-range electron-phonon interaction and to calculating the high-energy part of the angle-resolved photoemission spectroscopy (ARPES) spectra of such systems is suggested. Joint relaxation of strongly coupled fields-a field of correlated electrons and phonon field-after photoemission is studied to clarify the nature of characteristic features observed in the high-energy part of the ARPES spectra of cuprate superconductors. Such relaxation occurs in systems with strong predominantly long-range electron-phonon interaction at sufficiently high carrier concentration due to the coexistence of autolocalized and delocalized carriers. A simple method to calculate analytically a high-energy part of the ARPES spectrum arising is proposed. It takes advantage of using the coherent states basis for the phonon field in the polaron and bipolaron states. The approach suggested yields all the high-energy spectral features like broad Gaussian band and regions of 'vertical dispersion' being in good quantitative agreement with the experiments on cuprates at any doping with both types of carriers. Demonstrated coexistence of autolocalized and delocalized carriers in superconducting cuprates changes the idea about their ground state above the superconducting transition temperature that is important for understanding transport and magnetic properties. High density of large-radius autolocalized carriers revealed may be a key to the explanation of charge ordering in doped cuprates.
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Affiliation(s)
- A E Myasnikova
- Physics Faculty, Southern Federal University, Rostov-on-Don, Russia
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Peli S, Dal Conte S, Comin R, Nembrini N, Ronchi A, Abrami P, Banfi F, Ferrini G, Brida D, Lupi S, Fabrizio M, Damascelli A, Capone M, Cerullo G, Giannetti C. Mottness at finite doping and charge-instabilities in cuprates. NATURE PHYSICS 2017; 13:806-811. [PMID: 28781605 PMCID: PMC5540185 DOI: 10.1038/nphys4112] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 03/27/2017] [Indexed: 05/31/2023]
Abstract
The influence of the Mott physics on the doping-temperature phase diagram of copper oxides represents a major issue that is subject of intense theoretical and experimental effort. Here, we investigate the ultrafast electron dynamics in prototypical single-layer Bi-based cuprates at the energy scale of the O-2p→Cu-3d charge-transfer (CT) process. We demonstrate a clear evolution of the CT excitations from incoherent and localized, as in a Mott insulator, to coherent and delocalized, as in a conventional metal. This reorganization of the high-energy degrees of freedom occurs at the critical doping pcr ≈0.16 irrespective of the temperature, and it can be well described by dynamical mean field theory calculations. We argue that the onset of the low-temperature charge instabilities is the low-energy manifestation of the underlying Mottness that characterizes the p < pcr region of the phase diagram. This discovery sets a new framework for theories of charge order and low-temperature phases in underdoped copper oxides.
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Affiliation(s)
- S Peli
- Department of Mathematics and Physics, Università Cattolica del Sacro Cuore, Brescia I-25121, Italy
- Department of Physics, Università degli Studi di Milano, 20133 Milano, Italy
| | - S Dal Conte
- IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, 20133 Milano, Italy
| | - R Comin
- Quantum Matter Institute, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - N Nembrini
- Department of Mathematics and Physics, Università Cattolica del Sacro Cuore, Brescia I-25121, Italy
- Department of Physics, Università degli Studi di Milano, 20133 Milano, Italy
| | - A Ronchi
- Department of Mathematics and Physics, Università Cattolica del Sacro Cuore, Brescia I-25121, Italy
- I-LAMP (Interdisciplinary Laboratories for Advanced Materials Physics), Università Cattolica del Sacro Cuore, Brescia I-25121, Italy
- Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Heverlee, Leuven, Belgium
| | - P Abrami
- Department of Mathematics and Physics, Università Cattolica del Sacro Cuore, Brescia I-25121, Italy
- I-LAMP (Interdisciplinary Laboratories for Advanced Materials Physics), Università Cattolica del Sacro Cuore, Brescia I-25121, Italy
| | - F Banfi
- Department of Mathematics and Physics, Università Cattolica del Sacro Cuore, Brescia I-25121, Italy
- I-LAMP (Interdisciplinary Laboratories for Advanced Materials Physics), Università Cattolica del Sacro Cuore, Brescia I-25121, Italy
| | - G Ferrini
- Department of Mathematics and Physics, Università Cattolica del Sacro Cuore, Brescia I-25121, Italy
- I-LAMP (Interdisciplinary Laboratories for Advanced Materials Physics), Università Cattolica del Sacro Cuore, Brescia I-25121, Italy
| | - D Brida
- IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, 20133 Milano, Italy
- Department of Physics and Center for Applied Photonics, University of Konstanz, 78457 Konstanz, Germany
| | - S Lupi
- CNR-IOM Dipartimento di Fisica, Università di Roma La Sapienza P.le Aldo Moro 2, 00185 Rome, Italy
| | - M Fabrizio
- Scuola Internazionale Superiore di Studi Avanzati (SISSA) and CNR-IOM Democritos National Simulation Center, Via Bonomea 265, 34136 Trieste (Italy)
| | - A Damascelli
- Quantum Matter Institute, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - M Capone
- Scuola Internazionale Superiore di Studi Avanzati (SISSA) and CNR-IOM Democritos National Simulation Center, Via Bonomea 265, 34136 Trieste (Italy)
| | - G Cerullo
- IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, 20133 Milano, Italy
| | - C Giannetti
- Department of Mathematics and Physics, Università Cattolica del Sacro Cuore, Brescia I-25121, Italy
- I-LAMP (Interdisciplinary Laboratories for Advanced Materials Physics), Università Cattolica del Sacro Cuore, Brescia I-25121, Italy
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Electronic evidence of an insulator-superconductor crossover in single-layer FeSe/SrTiO3 films. Proc Natl Acad Sci U S A 2014; 111:18501-6. [PMID: 25502774 DOI: 10.1073/pnas.1414094112] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In high-temperature cuprate superconductors, it is now generally agreed that superconductivity is realized by doping an antiferromagnetic Mott (charge transfer) insulator. The doping-induced insulator-to-superconductor transition has been widely observed in cuprates, which provides important information for understanding the superconductivity mechanism. In the iron-based superconductors, however, the parent compound is mostly antiferromagnetic bad metal, raising a debate on whether an appropriate starting point should go with an itinerant picture or a localized picture. No evidence of doping-induced insulator-superconductor transition (or crossover) has been reported in the iron-based compounds so far. Here, we report an electronic evidence of an insulator-superconductor crossover observed in the single-layer FeSe film grown on a SrTiO3 substrate. By taking angle-resolved photoemission measurements on the electronic structure and energy gap, we have identified a clear evolution of an insulator to a superconductor with increasing carrier concentration. In particular, the insulator-superconductor crossover in FeSe/SrTiO3 film exhibits similar behaviors to that observed in the cuprate superconductors. Our results suggest that the observed insulator-superconductor crossover may be associated with the two-dimensionality that enhances electron localization or correlation. The reduced dimensionality and the interfacial effect provide a new pathway in searching for new phenomena and novel superconductors with a high transition temperature.
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Witnessing the formation and relaxation of dressed quasi-particles in a strongly correlated electron system. Nat Commun 2014; 5:5112. [PMID: 25290587 DOI: 10.1038/ncomms6112] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 09/02/2014] [Indexed: 11/08/2022] Open
Abstract
The non-equilibrium approach to correlated electron systems is often based on the paradigm that different degrees of freedom interact on different timescales. In this context, photo-excitation is treated as an impulsive injection of electronic energy that is transferred to other degrees of freedom only at later times. Here, by studying the ultrafast dynamics of quasi-particles in an archetypal strongly correlated charge-transfer insulator (La2CuO(4+δ)), we show that the interaction between electrons and bosons manifests itself directly in the photo-excitation processes of a correlated material. With the aid of a general theoretical framework (Hubbard-Holstein Hamiltonian), we reveal that sub-gap excitation pilots the formation of itinerant quasi-particles, which are suddenly dressed by an ultrafast reaction of the bosonic field.
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Peng Y, Meng J, Mou D, He J, Zhao L, Wu Y, Liu G, Dong X, He S, Zhang J, Wang X, Peng Q, Wang Z, Zhang S, Yang F, Chen C, Xu Z, Lee TK, Zhou XJ. Disappearance of nodal gap across the insulator-superconductor transition in a copper-oxide superconductor. Nat Commun 2014; 4:2459. [PMID: 24051514 DOI: 10.1038/ncomms3459] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 08/18/2013] [Indexed: 11/09/2022] Open
Abstract
The parent compound of the copper-oxide high-temperature superconductors is a Mott insulator. Superconductivity is realized by doping an appropriate amount of charge carriers. How a Mott insulator transforms into a superconductor is crucial in understanding the unusual physical properties of high-temperature superconductors and the superconductivity mechanism. Here we report high-resolution angle-resolved photoemission measurement on heavily underdoped Bi₂Sr₂-xLaxCuO(₆+δ) system. The electronic structure of the lightly doped samples exhibit a number of characteristics: existence of an energy gap along the nodal direction, d-wave-like anisotropic energy gap along the underlying Fermi surface, and coexistence of a coherence peak and a broad hump in the photoemission spectra. Our results reveal a clear insulator-superconductor transition at a critical doping level of ~0.10 where the nodal energy gap approaches zero, the three-dimensional antiferromagnetic order disappears, and superconductivity starts to emerge. These observations clearly signal a close connection between the nodal gap, antiferromagnetism and superconductivity.
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Affiliation(s)
- Yingying Peng
- National Laboratory for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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8
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Peng WW, Niu G, Tétot R, Vilquin B, Raimondi F, Brubach JB, Amzallag E, Yanagida T, Autier-Laurent S, Lecoeur P, Roy P. Insulator-metal transition of VO₂ ultrathin films on silicon: evidence for an electronic origin by infrared spectroscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:445402. [PMID: 24121423 DOI: 10.1088/0953-8984/25/44/445402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report on the first simultaneous observations of both electronic and structural temperature-induced insulator-to-metal transition (IMT) in VO2 ultrathin films, made possible by the use of broad range transmission infrared spectroscopy. Thanks to these techniques, the infrared phonon structures, as well as the appearance of the free carrier signature, were resolved for the first time. The temperature-resolved spectra allowed the determination of the temperature hysteresis for both the structural (monoclinic-to-rutile) and electronic (insulator-to-metallic) transitions. The combination of these new observations and DFT simulations for the monoclinic structure allows us to verify the direct transition from monoclinic (M1) to rutile and exclude an intermediate structural monoclinic form (M2). The delay in structural modification compared to the primer electronic transition (325 K compared to 304 K) supports the role of free charges as the transition driving force. The shape of the free charge hysteresis suggests that the primer electronic transition occurs first at 304 K, followed by both its propagation to the heart of the layer and the structural transition when T increases. This study outlines further the potential of VO2 ultrathin films integrated on silicon for optoelectronics and microelectronics.
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Affiliation(s)
- W W Peng
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette, France
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De Filippis G, Cataudella V, Nowadnick EA, Devereaux TP, Mishchenko AS, Nagaosa N. Quantum dynamics of the Hubbard-Holstein model in equilibrium and nonequilibrium: application to pump-probe phenomena. PHYSICAL REVIEW LETTERS 2012; 109:176402. [PMID: 23215207 DOI: 10.1103/physrevlett.109.176402] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Indexed: 06/01/2023]
Abstract
The spectral response and physical features of the 2D Hubbard-Holstein model are calculated both in equilibrium at zero and low chemical dopings, and after an ultrashort powerful light pulse, in undoped systems. At equilibrium and at strong charge-lattice couplings, the optical conductivity reveals a three-peak structure in agreement with experimental observations. After an ultrashort pulse and at nonzero electron-phonon interaction, phonon and spin subsystems oscillate with the phonon period T(ph)≈80 fs. The decay time of the phonon oscillations is about 150-200 fs, similar to the relaxation time of the charge system. We propose a criterion for observing these oscillations in high T(c) compounds: the time span of the pump light pulse τ(pump) has to be shorter than the phonon oscillation period T(ph).
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Affiliation(s)
- G De Filippis
- SPIN-CNR and Dipartimento di Scienze Fisiche-Università di Napoli Federico II-I-80126 Napoli, Italy
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Perucchi A, Baldassarre L, Nucara A, Calvani P, Adamo C, Schlom DG, Orgiani P, Maritato L, Lupi S. Optical properties of (SrMnO₃)n/(LaMnO₃)₂n superlattices: an insulator-to-metal transition observed in the absence of disorder. NANO LETTERS 2010; 10:4819-4823. [PMID: 21058711 DOI: 10.1021/nl1022628] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We measure the optical conductivity, σ1(ω), of (SrMnO3)n/(LaMnO3)2n superlattices (SL) for n = 1, 3, 5, and 8 and 10 < T < 400 K. Data show a T-dependent insulator to metal transition (IMT) for n ≤ 3, driven by the softening of a polaronic mid-infrared band. At n = 5 that softening is incomplete, while at the largest-period n = 8 compound the MIR band is independent of T and the SL remains insulating. One can thus first observe the IMT in a Manganite system in the absence of the disorder due to chemical doping. Unsuccessful reconstruction of the SL optical properties from those of the original bulk materials suggests that (SrMnO3)n/(LaMnO3)2n heterostructures give rise to a novel electronic state.
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Affiliation(s)
- Andrea Perucchi
- Sincrotrone Trieste, Area Science Park, I-34012 Trieste, Italy
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Nicoletti D, Limaj O, Calvani P, Rohringer G, Toschi A, Sangiovanni G, Capone M, Held K, Ono S, Ando Y, Lupi S. High-temperature optical spectral weight and fermi-liquid renormalization in bi-based cuprate superconductors. PHYSICAL REVIEW LETTERS 2010; 105:077002. [PMID: 20868070 DOI: 10.1103/physrevlett.105.077002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Indexed: 05/29/2023]
Abstract
The optical conductivity σ(ω) and the spectral weight W(T) of two superconducting cuprates at optimum doping, Bi2Sr2-xLaxCuO6 and Bi2Sr2CaCu2O8, have been first measured up to 500 K. Above 300 K, W(T) deviates from the usual T2 behavior in both compounds, even though σ(ω→0) remains larger than the Ioffe-Regel limit. The deviation is surprisingly well described by the T4 term of the Sommerfeld expansion, but its coefficients are enhanced by strong correlation, as shown by the good agreement with dynamical mean field calculations.
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Affiliation(s)
- D Nicoletti
- CNR-SPIN and Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale A. Moro 2, I-00185 Roma, Italy
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