Enhancing Tc in a composite superconductor/metal bilayer system: A dynamical cluster approximation study

It has been proposed that the superconducting transition temperature T-c of an unconventional superconductor with a large pairing scale but strong phase fluctuations can be enhanced by coupling it to a metal. However, the general efficacy of this approach across different parameter regimes remains an open question. Using the dynamical cluster approximation, we study this question in a system composed of an attractive Hubbard layer in the intermediate coupling regime, where the magnitude of the attractive Coulomb interaction vertical bar U vertical bar is slightly larger than the bandwidth W, hybridized with a noninteracting metallic layer. We find that while the superconducting transition becomes more mean-field-like with increasing interlayer hopping, the superconducting transition temperature T-c exhibits a nonmonotonic dependence on the strength of the hybridization t(perpendicular to). This behavior arises from a reduction of the effective pairing interaction in the correlated layer that outcompetes the growth in the intrinsic pair-field susceptibility induced by the coupling to the metallic layer. We find that the largest T-c inferred here for the composite system is comparable to the maximum value currently estimated for the isolated negative-U Hubbard model.

Automated summary

This study investigates the effect of coupling a metal on the superconducting transition temperature of an unconventional superconductor. The results show a nonmonotonic dependence of the transition temperature on the strength of hybridization and interlayer hopping.