Superfluid stiffness renormalization and critical temperature enhancement in a composite superconductor

Article

关键词: U HUBBARD-MODEL;    MONTE-CARLO;    TRANSITION;    SYSTEMS;    FLUCTUATIONS;    INSULATOR;    JUNCTIONS;    DYNAMICS;    FILMS;   

DOI  :  10.1103/PhysRevB.86.134531

来源: SCIE

【 摘 要 】

We study a model of a composite system constructed from a pairing layer of disconnected attractive-U Hubbard sites that is coupled by single-particle tunneling, t(perpendicular to), to a disordered metallic layer. For small interlayer tunneling the system is described by an effective long-range XY phase model whose critical temperature, T-c, is essentially insensitive to the disorder and is exponentially suppressed by quantum fluctuations. T-c reaches a maximum for intermediate values of t(perpendicular to), which we calculate using a combination of mean-field, classical, and quantum Monte Carlo methods. The maximal T-c scales as a fraction of the zero-temperature gap of the attractive sites when U is smaller than the metallic bandwidth, and is bounded by the maximal T-c of the two-dimensional attractive Hubbard model for large U. Our results indicate that a thin, rather than a thick, metallic coating is better suited for the enhancement of T-c at the surface of a phase fluctuating superconductor.

【 授权许可】

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