Evolution of the dynamics of neutral superconductors between BCS and BEC regimes: The variational approach

Chubukov, Andrey V.

doi:10.1063/1.5037555

Cited by 3 publications

(3 citation statements)

References 60 publications

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“…independent on the ratio E 0 /E F . The same result (the independence of E cond on E 0 /E F ) has been also obtained 24,33 by directly evaluating the kinetic and the potential energy of a superconductor.…”

Section: A the Condensation Energysupporting

confidence: 68%

“…Such force is typically attributed to the terms in the effective action that are linear in time derivatives of the phase, i.e., proportional to drdτ φ. This term is often referred to in the literature as Berry phase term 25,[27][28][29][30][31][32][33] . It reduces to the contribution from a boundary and does not contribute to the dynamics if φ is well defined at any r and τ .…”

Section: Introductionmentioning

confidence: 99%

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Dynamic properties of superconductors: Anderson-Bogoliubov mode and Berry phase in the BCS and BEC regimes

Chubukov

2019

Phys. Rev. B

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We analyze the evolution of the dynamics of a neutral s-wave superconductor between BCS and BEC regimes. We consider 2d case, when BCS-BEC crossover occurs already at weak coupling as a function of the ratio of the two scales -the Fermi energy EF and the bound state energy for two fermions in a vacuum, E0. BCS and BEC limits correspond to EF ≫ E0 and EF ≪ E0, respectively. The chemical potential µ = EF − E0 changes the sign between the two regimes. We use the effective action approach, derive the leading terms in the expansion of the effective action in the spatial and time derivative of the slowly varying superconducting order parameter ∆(r, τ ), and express the action in terms of derivative of the phase φ(r, τ ) of ∆(r, τ ) = ∆e iφ(r,τ ) . The action contains (∇φ) 2 andφ 2 terms, which determine the dispersion of collective phase fluctuations, and iπAφ term. For continuous φ(r, τ ), the latter reduces to the contribution from the boundary and does not affect the dynamics. We show that this longwavelength action does not change through BCS-BEC crossover. We apply our approach to a moving vortex, for which φ is singular at the center of the vortex core, and iπAvortφ term affects vortex dynamics. We find that this term has two contributions. One comes from the states away from the vortex core and has Avort,1 = n/2, where n is the fermion density. The other comes from electronic states inside the vortex core and has Avort,2 = −n0/2, where n0 is the fermion density at the vortex core. This last term comes from the continuous part of the electronic spectrum and has no contribution from discrete levels inside the core; it also does not change if we add impurities. We interpret this term as the contribution to vortex dynamics in the continuum limit, when the spacing between energy levels ω is set to zero, while fermionic lifetime τ can be arbitrary. The total Avort = (n − n0)/2 determines the transversal force acting on the vortex core, πAvortṘ ×ẑ, whereṘ is the velocity of the vortex core andẑ a unit vector perpendicular to the 2d sample. The difference (n − n0)/2 changes through the BEC-BCS crossover as n0 nearly compensates n in the BCS regime, but vanishes in the BEC regime.

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Section: A the Condensation Energysupporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Dynamic properties of superconductors: Anderson-Bogoliubov mode and Berry phase in the BCS and BEC regimes

Chubukov

2019

Phys. Rev. B

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“…In this work we present the scenario of roomtemperature superconductivity in pressurized hydrides due to a Fano-Feshbach resonance in multigap superconductivity near a Lifshitz transition [86][87][88][89][90][91][92][93][94][95][96][97][98]. A key feature of our approach is the calculation of exchange integrals, obtained by the overlap of the wave-functions of electrons in different Fermi surfaces calculated from first principles and the renormalization of the chemical potential at the Lifshitz transition with the opening of a new superconducting gap controlled by constraints of the density equation.…”

Section: Introductionmentioning

confidence: 99%

Resonant multigap superconductivity at room temperature near a Lifshitz topological transition in sulfur hydrides

Mazziotti,

Raimondi,

Valletta

et al. 2021

Preprint

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Resonant multi-gap superconductivity at room temperature near a Lifshitz topological transition in sulfur hydrides

Mazziotti

Raimondi

Valletta

et al. 2021

Journal of Applied Physics

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The maximum critical temperature for superconductivity in pressurized hydrides appears at the top of superconducting domes in Tc vs pressure curves at a particular pressure, which is not predicted by standard superconductivity theories. The high-order anisotropic Van Hove singularity near the Fermi level observed in band-structure calculations of pressurized sulfur hydride, typical of a supermetal, has been associated with the array of metallic hydrogen wire modules forming a nanoscale heterostructure at an atomic limit called the superstripe phase. Here, we propose that pressurized sulfur hydrides behave as a heterostructure made of a nanoscale superlattice of interacting quantum wires with a multicomponent electronic structure. We present first-principles quantum calculation of a universal superconducting dome where Tc amplification in multi-gap superconductivity is driven by the Fano–Feshbach resonance due to a configuration interaction between open and closed pairing channels, i.e., between multiple gaps in the BCS regime, resonating with a single gap in the BCS–Bose–Einstein condensation crossover regime. In the proposed three dimensional phase diagram, the critical temperature shows a superconducting dome where Tc is a function of two variables: (i) the Lifshitz parameter (η) measuring the separation of the chemical potential from the Lifshitz transition normalized by the inter-wire coupling and (ii) the effective electron–phonon coupling (g) in the appearing new Fermi surface including phonon softening. The results will be of help for material design of room-temperature superconductors at ambient pressure.

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Evolution of the dynamics of neutral superconductors between BCS and BEC regimes: The variational approach

Cited by 3 publications

References 60 publications

Dynamic properties of superconductors: Anderson-Bogoliubov mode and Berry phase in the BCS and BEC regimes

Dynamic properties of superconductors: Anderson-Bogoliubov mode and Berry phase in the BCS and BEC regimes

Resonant multigap superconductivity at room temperature near a Lifshitz topological transition in sulfur hydrides

Resonant multi-gap superconductivity at room temperature near a Lifshitz topological transition in sulfur hydrides

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