Crossover from BCS to Bose superconductivity: Transition temperature and time-dependent Ginzburg-Landau theory

Melo, C. A. R. Sá de; Randeria, Mohit; Engelbrecht, Jan R.

doi:10.1103/physrevlett.71.3202

Cited by 844 publications

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“…The importance of the strong coupling superconductivity has been pointed out by Randeria et al 20) on the basis of the Nozières and Schmitt-Rink (NSR) theory. 44,45) The NSR theory describes the crossover from the conventional BCS superconductivity to the Bose condensation of tightly-bound pre-formed pairs.…”

Section: §1 Introductionmentioning

confidence: 99%

“…The NSR theory has been investigated by many authors because the gap in the fermionic excitations is considered to be the pseudogap. 20,24,25,26,27) The existence of the pre-formed pairs has been proposed phenomenologically by Geshkenbein et al 28) with reference to the sign problem of the fluctuational Hall effect. 46) The strength of the superconducting coupling is indicated by the ratio T MF c /ε F .…”

Section: §1 Introductionmentioning

confidence: 99%

“…14) The tunneling spectroscopy have also shown the smooth change from the pseudogap state to the superconducting state. 13) The close relation between the pseudogap state and the superconducting state clearly indicates that the pseudogap is a precursor of the superconductivity.The paring scenarios have been proposed 20,21) and actively investigated in recent years. 19,22,23,24,25,26,27,28,29,30,31,32,33,34,3 They are classified into some kinds.…”

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Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-T_cCuprates

2001

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The pseudogap phenomena in High-Tc cuprates are investigated on the basis of the Hubbard model which includes only the on-site repulsive interaction U . We consider the pairing scenario for the pseudogap. The pseudogap arises from the resonance scattering due to the strong superconducting fluctuations. First, the electronic state and the anti-ferromagnetic spin fluctuations are calculated by using the fluctuation exchange (FLEX) approximation. The T-matrix which is the propagator of the superconducting fluctuations is calculated by extending theÉliashberg equation. The characteristics of the superconducting fluctuations due to the pairing interaction arising from the spin fluctuations are represented in the T-matrix. The self-energy due to the superconducting fluctuations is calculated by the T-matrix approximation. The pseudogap is shown in the single particle properties and the magnetic properties. Moreover, a comprehensive explanation of the doping dependence of the pseudogap is obtained. Furthermore, we apply the theory to the electron-doped cuprates and obtain the consistent results with the recent experiments. Finally, the self-consistent calculation for the spin fluctuations, superconducting fluctuations and the single particle properties are carried out within the FLEX and the self-consistent T-matrix approximations. The relation between the superconducting fluctuations and the spin fluctuations are clarified. The calculated superconducting critical temperature Tc is remarkably reduced from the results of the mean field (FLEX) calculation. In particular, it is shown that the critical temperature decreases with decreasing doping in the under-doped region with large U . The pseudogap phenomena in under-doped High-T c cuprates have been interested for many years. The pseudogap is considered to be a key issue for the comprehensive understanding of the High-T c superconductivity.The pseudogap phenomena mean the suppression of the spectral weight above T c without any long range order. They are universal phenomena observed in various compounds of High-T c cuprates in the under-doped region. First, the pseudogap was found in the magnetic excitation channel by the nuclear magnetic resonance (NMR) experiment. 1) At present, the pseudogap phenomena have been observed in various quantities which include NMR, 1, 2, 3, 4, 5, 6, 7) neutron scattering, 8) transport, 9, 10) optical spectrum, 11) electronic specific heat, 12) density of states 13) and the single particle spectral weight. 14) The experimental results are reviewed in ref. 15.There are many theoretical scenarios proposed for the pseudogap phenomena. An important one is the resonating valence bond (RVB) theory. The RVB theory is an approach from the non-Fermi liquid state and attributes the pseudogap to the singlet pairing of the spinons. 16) As an approach from the Fermi liquid state, the magnetic * E-mail: yanase@hosi.phys.s.u-tokyo.ac.jp * * Present address: Department of Physics, University of Tokyo, Tokyo 113-0033 scenario has been investigated. 17,18) ...

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Section: §1 Introductionmentioning

confidence: 99%

Section: §1 Introductionmentioning

confidence: 99%

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Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-T_cCuprates

2001

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“…Statements about binding energies of the pairs χ x,↑ (t p ) χ x,↓ (t p ) can be calculated by various saddle point considerations from the coherent state path integral (24) [25,26]. However, the exact expression of the saddle point is not needed for the derivation of the nonlinear sigma model with actions (54) and (55) for the time development of a condensate composed of fermionic atoms.…”

Section: Summary and Discussionmentioning

confidence: 99%

Nonlinear sigma model for a condensate composed of fermionic atoms

Mieck

2005

Physica A: Statistical Mechanics and its Applications

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A nonlinear sigma model is derived for the time development of a Bose-Einstein condensate composed of fermionic atoms. Spontaneous symmetry breaking of a Sp(2) symmetry in a coherent state path integral with anticommuting fields yields Goldstone bosons in a Sp(2)\U (2) coset space. After a Hubbard-Stratonovich transformation from the anticommuting fields to a local self-energy matrix with anomalous terms, the assumed short-ranged attractive interaction reduces this symmetry to a SO(4)\U (2) coset space with only one complex Goldstone field for the singlett pairs of fermions. This bosonic field for the anomalous term of fermions is separated in a gradient expansion from the density terms. The U (2) invariant density terms are considered as a background field or unchanged interacting Fermi sea in the spontaneous symmetry breaking of the SO(4) invariant action and appear as coefficients of correlation functions in the nonlinear sigma model for the Goldstone boson. The time development of the condensate composed of fermionic atoms results in a modified Sine-Gordon equation.

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“…For small concentrations of the carriers we have previously obtained the critical temperature [20] using the approach developed by Nozières and Schmitt-Rink [24] (see also [38,39]), while for the high density case we employ a new method similar to that used in [37].…”

Section: Superconducting Transition Into the Phase With Long-ranmentioning

confidence: 99%

Superconducting condensate formation in quasi-2D systems with arbitrary carrier density

Локтев

Quick

Sharapov

1999

Physica C: Superconductivity

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A phase diagram for a quasi-2D metal with variable carrier density has been derived. The phases present are the normal phase, where the order parameter is zero; the pseudogap phase where the absolute value of the order parameter is non-zero but its phase is random, and a superconducting phase with a crossover quasi-2D Berezinskii-KosterlitzThouless (BKT) region. The crossover region is bounded by the quasi-2D BKT temperature and the temperature for the onset of conventional long-range order (CLRO). The practical observation of these regions however critically depends on the carrier density. At high densities both the pseudogap and BKT regions vanish asymptotically i.e. one obtains the standard BCS picture. At intermediate densities the pseudogap phase is large but the BKT region negligible. Finally at very low densities both the pseudogap and BKT regions are sizeable. An attempt is made to explain the behaviour observed in underdoped (intermediate densities) and optimally doped high-Tc superconducting compounds above their critical temperature. The transition to the pseudogap phase should also be regarded as a crossover. 74.20.Fg, 74.20.Mn, 64.60.Cn

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Crossover from BCS to Bose superconductivity: Transition temperature and time-dependent Ginzburg-Landau theory

Cited by 844 publications

References 13 publications

Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-T_cCuprates

Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-T_cCuprates

Nonlinear sigma model for a condensate composed of fermionic atoms

Superconducting condensate formation in quasi-2D systems with arbitrary carrier density

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Crossover from BCS to Bose superconductivity: Transition temperature and time-dependent Ginzburg-Landau theory

Cited by 844 publications

References 13 publications

Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-TcCuprates

Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-TcCuprates

Nonlinear sigma model for a condensate composed of fermionic atoms

Superconducting condensate formation in quasi-2D systems with arbitrary carrier density

Contact Info

Product

Resources

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Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-T_cCuprates

Pseudogap Phenomena and Superconducting Fluctuations in Hubbard Model for High-T_cCuprates