Palestini, Pieri, and Strinati Reply:

Palestini, F.; Pieri, P.; Strinati, G. C.

doi:10.1103/physrevlett.109.118902

Cited by 61 publications

(116 citation statements)

References 4 publications

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“…[25]), with changes of T c related to the widening of conduction band by disorder. These results are also consistent with recent lowest order perturbation theory analysis of the effects of disorder throughout BCS-BEC crossover region [26].…”

Section: Discussionsupporting

confidence: 92%

Normal phase and superconducting instability in the attractive Hubbard model: a DMFT(NRG) study

Kuleeva

Kuchinskiǐ

Sadovskiǐ

2014

J. Exp. Theor. Phys.

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We study the normal (non-superconducting) phase of attractive Hubbard model within dynamical mean field theory (DMFT) using numerical renormalization group (NRG) as impurity solver. Wide range of attractive potentials U is considered, from the weak-coupling limit, where superconducting instability is well described by BCS approximation, up to the strong-coupling region, where superconducting transition is described by Bose-condensation of compact Cooper pairs, which are formed at temperatures much exceeding superconducting transition temperature. We calculate density of states, spectral density and optical conductivity in the normal phase for this wide range of U , including the disorder effects. Also we present the results on superconducting instability of the normal state dependence on the attraction strength U and the degree of disorder. Disorder influence on the critical temperature Tc is rather weak, suggesting in fact the validity of Anderson theorem, with the account of the general widening of the conduction band due to disorder.

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Section: Discussionsupporting

confidence: 92%

Normal phase and superconducting instability in the attractive Hubbard model: a DMFT(NRG) study

Kuleeva

Kuchinskiǐ

Sadovskiǐ

2014

J. Exp. Theor. Phys.

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“…For this discrepancy between the theory and experiment [53], although further analyses would be necessary, we note that Refs. [55,56] have recently pointed out that the experimental result may be understood by taking into account the non-equilibrium state associated with a quasi-repulsive interaction.…”

Section: Spin Susceptibility In the Bcs-bec Crossover Regionmentioning

confidence: 99%

Spin susceptibility and fluctuation corrections in the BCS-BEC crossover regime of an ultracold Fermi gas

2012

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We investigate magnetic properties and effects of pairing fluctuations in the BCS (BardeenCooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover regime of an ultracold Fermi gas.Recently, Liu and Hu, and Parish, pointed out that the strong-coupling theory developed by Nozières and Schmitt-Rink (NSR), which has been extensively used to successfully clarify various physical properties of cold Fermi gases, unphysically gives negative spin susceptibility in the BCS-BEC crossover region. The same problem is found to also exist in the ordinary non-self-consistent T -matrix approximation. In this paper, we clarify that this serious problem comes from incomplete treatment in term of pseudogap phenomena originating from strong pairing fluctuations, as well as effects of spin fluctuations on the spin susceptibility. Including these two key issues, we construct an extended T -matrix theory which can overcome this problem. The resulting positive spin susceptibility agrees well with the recent experiment on a 6 Li Fermi gas done by Sanner and co-workers. We also apply our theory to a polarized Fermi gas to examine the superfluid phase transition temperature T c , as a function of the polarization rate. Since the spin susceptibility is an important physical quantity, especially in singlet Fermi superfluids, our results would be useful in considering how singlet pairs appear above and below T c in the BCS-BEC crossover regime of cold Fermi gases.

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“…On the theory side, the dynamic response functions and the structure factors were calculated by using the random phase approximation (RPA) [60,61] and the pseudogap theory [62], which showed qualitative agreement with experimental measurements. A diagrammatic approach to study the dynamic responses in the normal phase was also proposed [63] but so far only the static compressibility and the spin susceptibility have been reported. In the high temperature regime, the dynamic structure factors were studied by using the virial expansion [64,65].…”

mentioning

confidence: 99%

Dynamic density and spin responses of a superfluid Fermi gas in the BCS–BEC crossover: Path integral formulation and pair fluctuation theory

2016

Annals of Physics

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We present a standard field theoretical derivation of the dynamic density and spin linear response functions of a dilute superfluid Fermi gas in the BCS-BEC crossover in both three and two dimensions. The derivation of the response functions is based on the elegant functional path integral approach which allows us to calculate the density-density and spin-spin correlation functions by introducing the external sources for the density and the spin density. Since the generating functional cannot be evaluated exactly, we consider two gapless approximations which ensure a gapless collective mode (Goldstone mode) in the superfluid state: the BCS-Leggett mean-field theory and the Gaussian-pair-fluctuation (GPF) theory. In the mean-field theory, our results of the response functions agree with the known results from the random phase approximation. We further consider the pair fluctuation effects and establish a theoretical framework for the dynamic responses within the GPF theory. We show that the GPF response theory naturally recovers three kinds of famous diagrammatic contributions: the Self-Energy contribution, the Aslamazov-Lakin contribution, and the Maki-Thompson contribution. We also show that unlike the equilibrium state, in evaluating the response functions, the linear (first-order) terms in the external sources as well as the induced order parameter perturbations should be treated carefully. In the superfluid state, there is an additional order parameter contribution which ensures that in the static and long wavelength limit, the density response function recovers the result of the compressibility (compressibility sum rule). We expect that the f -sum rule is manifested by the full number equation which includes the contribution from the Gaussian pair fluctuations. The dynamic density and spin response functions Preprint submitted to Annals of Physics (N. Y.) August 9, 2016 in the normal phase (above the superfluid critical temperature) are also derived within the Nozières-Schmitt-Rink (NSR) theory.

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Palestini, Pieri, and Strinati Reply:

Cited by 61 publications

References 4 publications

Normal phase and superconducting instability in the attractive Hubbard model: a DMFT(NRG) study

Normal phase and superconducting instability in the attractive Hubbard model: a DMFT(NRG) study

Spin susceptibility and fluctuation corrections in the BCS-BEC crossover regime of an ultracold Fermi gas

Dynamic density and spin responses of a superfluid Fermi gas in the BCS–BEC crossover: Path integral formulation and pair fluctuation theory

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