Bose condensation in an attractive fermion gas: From weak to strong coupling superconductivity

Nozières, P.; Schmitt‐Rink, S.

doi:10.1007/bf00683774

Cited by 1,829 publications

(2,236 citation statements)

References 6 publications

Supporting

Mentioning

2,136

Contrasting

Unclassified

Order By: Relevance

“…As a typical example, Fig. 3(a) shows the results obtained by Nozières and Schmitt-Rink [41] in 1985. Note that the horizontal axis is given for the coupling strength V , normalized to the "critical strength" V c related to the particle density and the range of the interaction.…”

Section: Be-bcs Crossover Conjecturementioning

confidence: 99%

Condensation, excitation, pairing, and superfluid density in high-T_c superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Uemura¹

2004

J. Phys.: Condens. Matter

100

123

View full text Add to dashboard Cite

To find out a primary determing factor of Tc and a pairing mechanism in high-Tc cuprates, we combine the muon spin relaxation results on ns/m * (superconducting carrier density / effective mass), accumulated over the last 15 years, with the results from neutron and Raman scattering, STM, specific heat, Nernst effect and ARPES measurements. We identify the neutron magnetic resonance mode as an analogue of roton minimum in the superfluid 4 He, and argue that ns/m * and the resonance mode energy ωres play a primary role in determining Tc in the underdoped region. We propose a picture that roton-like excitations in the cuprates appear as a coupled mode, which has the resonance mode for spin and charge responses at different momentum transfers but the same energy transfers, as detected respectively, by the neutron S=1 mode and the Raman S=0 A1g mode. We shall call this as the "hybrid spin/charge roton". After discussing the role of dimensionality in condensation, we propose a generic phase diagram of the cuprates with spatial phase separation in the overdoped region as a special case of the BE-BCS crossover conjecture where the superconducting coupling is lost rapidly in the overdoped region. Using a microscopic model of charge motion resonating with antiferomagnetic spin fluctuations, we propose a possibility that the hybrid spin/charge roton and higher-energy spin fluctuations mediate the superconducting pairing. In this model, the resonance modes can be viewed as a meson-analogue and the "dome" shape of the phase diagram can be understood as a natural consequence of departure from the competing Mott insulator ground state via carrier doping.

show abstract

Section: Be-bcs Crossover Conjecturementioning

confidence: 99%

Condensation, excitation, pairing, and superfluid density in high-T_c superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Uemura¹

2004

J. Phys.: Condens. Matter

100

123

View full text Add to dashboard Cite

show abstract

“…We have been arguing for some time now that pseudogap effects necessarily persist below T c , and moreover, appear to compete with superconductivity -despite their common origin. Our approach is based on a simple physical picture [11] which interpolates smoothly between BCS theory and Bose Einstein condensation, and on its realization as first studied by Leggett [12], Nozieres [13] and Randeria [14] and their respective co-workers. Our main contribution has been to extend the Leggett ground state picture to non zero temperatures in a self consistent fashion, so as to incorporate pseudogap effects which were absent in earlier finite temperature calculations.…”

Section: Cond-mat/0107275mentioning

confidence: 99%

The origin of the pseudogap phase: precursor superconductivity versus a competing energy gap scenario

Levin

Chen

Kosztin

et al. 2002

Journal of Physics and Chemistry of Solids

View full text Add to dashboard Cite

In the last few years evidence has been accumulating that there are a multiplicity of energy scales which characterize superconductivity in the underdoped cuprates. In contrast to the situation in BCS superconductors, the phase coherence temperature Tc is different from the energy gap onset temperature T * . In addition, thermodynamic and tunneling spectroscopies have led to the inference that the order parameter ∆sc is to be distinguished from the excitation gap ∆; in this way, pseudogap effects persist below Tc. It has been argued by many in the community that the presence of these distinct energy scales demonstrates that the pseudogap is unrelated to superconductivity. In this paper we show that this inference is incorrect. We demonstrate that the difference between the order parameter and excitation gap and the contrasting dependences of T * and Tc on hole concentration x and magnetic field H follow from a natural generalization of BCS theory. This simple generalized form is based on a BCS-like ground state, but with self consistently determined chemical potential in the presence of arbitrary attractive coupling g. We have applied this mean field theory with some success to tunneling, transport, thermodynamics and magnetic field effects. We contrast the present approach with the phase fluctuation scenario and discuss key features which might distinguish our precursor superconductivity picture from that involving a competing order parameter. cond-mat/0107275One of the biggest questions which faces the high temperature superconductivity community is determining the origin of the pseudogap phase. It is now becoming clear that pseudogap effects are not restricted to the normal state alone. Moreover, they appear to persist over a wide range of the phase diagram, up to and possibly above optimal doping [1]. Understanding the pseudogap phase is essential in order to find a proper replacement for BCS theory. Indeed, the failure of BCS theory is demonstrated most clearly in thermodynamical[2] and tunneling[3] data which have made it clear that the underlying normal phase below T c contains a (pseudo)gap in the excitation spectrum. The phase diagram, itself, indicates that the larger the pseudogap the lower is T c and in this way the pseudogap appears to compete with superconductivity. This competition has led many researchers to argue that T c and T * must necessarily originate from different physical mechanisms. A recent D-density wave (DDW) theory[4] presents a concrete realization of the "competing energy gap" scenario, first conjectured by Loram and co-workers [2].The present paper summarizes work from our group [5][6][7][8][9][10] which is based on a precursor superconductivity approach to understanding the pseudogap phase. We have been arguing for some time now that pseudogap effects necessarily persist below T c , and moreover, appear to compete with superconductivity -despite their common origin. Our approach is based on a simple physical picture [11] which interpolates smoothly between BCS theory and Bose Ei...

show abstract

“…Note that these equations are valid approximations not only in the BCS limit, encountered for largeñ or wheng is below the threshold to bind an isolated pair, but also in the opposite, Bose-Einstein condensation limit [32,33].…”

Section: Resultsmentioning

confidence: 99%

On the nature of the superconducting gap in the cuprates

Quintanilla¹,

Györffy²

2002

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

Recent experiments indicate that the excitation spectrum of the cuprates is characterised, in the superconducting state, by two energy scales: the "coherence energy" ∆ c and the "pseudogap" ∆ p . Here we consider a simple generalisation of the BCS model that yields exotic pairing and can describe, phenomenologically, the generic trends in the critical temperature T c of cuprate superconductors. We use the model to predict the gap in the single-particle spectrum arising from the superconductivity and we find evidence that it corresponds to the lower of the two energy scales, ∆ c , seen in the experiments. This provides further support to the view that the origin of the pseudogap is not superconducting fluctuations.

show abstract

Bose condensation in an attractive fermion gas: From weak to strong coupling superconductivity

Cited by 1,829 publications

References 6 publications

Condensation, excitation, pairing, and superfluid density in high-T_c superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Condensation, excitation, pairing, and superfluid density in high-T_c superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

The origin of the pseudogap phase: precursor superconductivity versus a competing energy gap scenario

On the nature of the superconducting gap in the cuprates

Contact Info

Product

Resources

About

Bose condensation in an attractive fermion gas: From weak to strong coupling superconductivity

Cited by 1,829 publications

References 6 publications

Condensation, excitation, pairing, and superfluid density in high-Tc superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Condensation, excitation, pairing, and superfluid density in high-Tc superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

The origin of the pseudogap phase: precursor superconductivity versus a competing energy gap scenario

On the nature of the superconducting gap in the cuprates

Contact Info

Product

Resources

About

Condensation, excitation, pairing, and superfluid density in high-T_c superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing

Condensation, excitation, pairing, and superfluid density in high-T_c superconductors: the magnetic resonance mode as a roton analogue and a possible spin-mediated pairing