Effect of inhomogeneous coupling on superconductivity

Abstract

We investigate the influence of inhomogeneity in the pairing coupling constant $U(\vec{r})$ on dirty BCS superconductors, focusing on $T_c$, the order parameter $\Delta (\vec{r})$, and the energy gap $E_g(\vec{r})$. Within mean-field theory, we find that when the length-scale of the inhomogeneity is comparable to, or larger than the coherence length, the ratio $2E_g/T_c$ is significantly reduced from that of a homogeneous superconductor, while in the opposite limit this ratio stays unmodified. In two dimensions, when strong phase fluctuations are included, the Kosterlitz-Thouless temperature $T_{KT}$ is also studied. We find that when the inhomogeneity length scale is much larger than the coherence length, $2E_g/T_{KT}$ can be larger than the usual BCS value. We use our results to qualitatively explain recent experimental observation of a surprisingly low value of $2E_g/T_c$ in thin films.

12 pages, 14 figures

References in corpus (22)

• Quasiclassical Green's function approach to mesoscopic superconductivity
• Nature of the superconductor-insulator transition in disordered superconductors
• Inhomogeneous Pairing in Highly Disordered s-wave Superconductors
• The superconductor-insulator transition in 2D dirty boson systems
• Dissipation effects on the superconductor-insulator transition in 2-D superconductors
• Superconductivity-Related Insulating Behavior
• Transport Through Quantum Melts
• Magnetically Induced Metallic Phase in Superconducting Tantalum Films
• Effects of dissipation on quantum phase transitions
• Vortices and quasiparticles near the "superconductor-insulator" transition in thin films
• Superconductive properties of thin dirty SN bilayers
• Quantum superconductor-metal transition
• Enhancement of superconductivity by local inhomogeneity
• True Superconductivity in a 2D "Superconducting-Insulating" System
• Theory of Magneto-resistance of Disordered Superconducting Films
• Gap Fluctuations in Inhomogeneous Superconductors
• Effect of inhomogeneity on s-wave superconductivity in the attractive Hubbard model
• Interaction-induced Bose Metal in 2D
• s-wave Superconductivity Phase Diagram in the Inhomogeneous Two-Dimensional Attractive Hubbard Model
• Observation of a subgap density of states in superconductor-normal metal bilayers in the Cooper limit
• "Super weakly" coupled superconductivity in ultrathin superconductor-normal-metal bilayers
• Early stage morphology of quench condensed Ag, Pb and Pb/Ag hybrid films

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• Influence of the atomic-scale inhomogeneity of the pair interaction on extracted from the STM spectra characteristics of high-$T_c$ superconductors
• The Low-Temperature Phenomenology of Gap Inhomogeneity in the Cuprate Superconductors: High-Energy Granularity, Low-Energy Homogeneity, and Spectral Kinks
• Surface density of states in superconductors with inhomogeneous pairing constant: Analytical results
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