TY - JOUR

T1 - Superfluid stiffness renormalization and critical temperature enhancement in a composite superconductor

AU - Wachtel, Gideon

AU - Bar-Yaacov, Assaf

AU - Orgad, Dror

PY - 2012/10/31

Y1 - 2012/10/31

N2 - 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, 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, 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.

AB - 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, 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, 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.

UR - http://www.scopus.com/inward/record.url?scp=84869049985&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.86.134531

DO - 10.1103/PhysRevB.86.134531

M3 - Article

AN - SCOPUS:84869049985

SN - 1098-0121

VL - 86

JO - Physical Review B - Condensed Matter and Materials Physics

JF - Physical Review B - Condensed Matter and Materials Physics

IS - 13

M1 - 134531

ER -