Going beyond the BCS level in the superfluid path integral: A consistent treatment of electrodynamics and thermodynamics

Anderson, Brandon; Boyack, Rufus; Wu, Chien‐Te; Levin, K.

doi:10.1103/physrevb.93.180504

Cited by 10 publications

(18 citation statements)

References 30 publications

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“…The origin of collective mode contributions to the Meissner effect [16,17] is due to the fact that, in the presence of a vector potential A µ , the order parameter ∆ will depend on A µ through the gap (saddle-point) equation [9,20]. A series expansion of ∆[A], in powers of A µ , is thus…”

Section: Introductionmentioning

confidence: 99%

Collective mode contributions to the Meissner effect: Fulde-Ferrell and pair-density wave superfluids

Boyack

Wu²,

Anderson

et al. 2017

Phys. Rev. B

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In this paper we demonstrate the necessity of including the generally omitted collective mode contributions in calculations of the Meissner effect for non-uniform superconductors. We consider superconducting pairing with non-zero center of mass momentum, as is possibly relevant to high transition temperature cuprates, cold atoms, and color superconductors in quantum chromodynamics. For the concrete example of the Fulde-Ferrell phase we present a quantitative calculation of the superfluid density, showing the collective mode contributions are not only appreciable but that they derive from the amplitude mode of the order parameter. This latter mode is generally viewed as being invisible in conventional superconductors. However, our analysis shows that it is extremely important in pair-density wave type superconductors, where it destroys superfluidity well before the mean-field order parameter vanishes.

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Section: Introductionmentioning

confidence: 99%

Collective mode contributions to the Meissner effect: Fulde-Ferrell and pair-density wave superfluids

Boyack

Wu²,

Anderson

et al. 2017

Phys. Rev. B

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“…When stronger-than-BCS attractive interaction is considered, the gauge invariance has to be maintained in a non-trivial way due to the pair fluctuation effects. There have been some formal discussions on this subject [27][28][29][30][31]. A general principle to find a gauge invariant interaction vertex is the same as proving WI in quantum field theory: inserting the bare EM vertex to the selfenergy diagram in all possible ways.…”

Section: Gauge Invariant Linear Response Theory With Pair Fluctuationmentioning

confidence: 99%

Dynamic density structure factor of a unitary Fermi gas at finite temperature

Guo

2018

J. Phys. Commun.

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We present a theoretical investigation of the dynamic density structure factor of a strongly interacting Fermi gas near the Feshbach resonance at finite temperature, which can be exploited in two photon Bragg scattering experiments. This study is based on a fully gauge invariant linear response theory, which is consistent with a diagrammatic approach for the equilibrium state taking into account the pair fluctuation effects and respects important restrictions like the f-sum rule. At small incoming momentum, the dynamic density structure factor exhibits various features including the Nambu-Goldstone-mode peak and the quasiparticle-scattering, pairing-breaking continua. At large incoming momentum and at half recoil frequency, the structure factor has a qualitatively similar behavior as the order parameter, which can signify the appearance of the condensate. These results qualitatively agree with the recent Bragg spectroscopy experiments.

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“…Here the single-particle dispersion (in momentum space) is ξ p = p 2 / (2m) − µ, and τ x , τ y , τ z are the standard Pauli matrices, with τ ± = 1 2 (τ x ± iτ y ). After integrating out the fermions the HS action is obtained [16,17,32]:…”

Section: A Hubbard-stratonovich Transformationmentioning

confidence: 99%

Restoring gauge invariance in conventional fluctuation corrections to a superconductor

Boyack

2018

Phys. Rev. B

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In this paper the complete set of diagrams for conventional fluctuation corrections to the normal state of a superconductor are derived using a functional-integral approach. The standard diagrams which characterize the fluctuation phase of a superconductor, namely Aslamazov-Larkin, Maki-Thompson, and Density of states, are obtained and proved to be insufficient to produce a gauge-invariant electromagnetic response. An additional diagram is derived, and it is found to be essential for rendering the theory gauge invariant, and for establishing the absence of the Meissner effect in the normal state. It is shown that, not only the Aslamazov-Larkin term, but all of the microscopic diagrams are encapsulated within a Gaussian-level treatment of the effective action. arXiv:1806.02438v1 [cond-mat.supr-con]

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Going beyond the BCS level in the superfluid path integral: A consistent treatment of electrodynamics and thermodynamics

Cited by 10 publications

References 30 publications

Collective mode contributions to the Meissner effect: Fulde-Ferrell and pair-density wave superfluids

Collective mode contributions to the Meissner effect: Fulde-Ferrell and pair-density wave superfluids

Dynamic density structure factor of a unitary Fermi gas at finite temperature

Restoring gauge invariance in conventional fluctuation corrections to a superconductor

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