Increase in d-Wave Superconducting Transition Temperature near Imperfect Layer in Correlated Electron System

TL;DR

This study demonstrates that an imperfect layer with a site potential in a correlated electron system can enhance the d-wave superconducting transition temperature by modifying the Fermi surface and increasing spin fluctuations.

Contribution

It reveals that site potential in an imperfect layer can independently increase the superconducting transition temperature in a d-wave superconductor, a novel insight into layered correlated systems.

Findings

Superconducting transition temperature of the imperfect layer exceeds that of the bulk.

Fermi surface nesting enhances antiferromagnetic spin fluctuations.

Density of states near the Fermi level increases, favoring d-wave pairing.

Abstract

The effect of the site potential in an imperfect layer is studied in a d-wave layer superconductor on the basis of the electron correlation. The site potential binds electrons to the imperfect layer, and then, the superconductivity of the imperfect layer is independent of that of the bulk. We found that the superconducting transition temperature of the imperfect layer becomes higher than that of the bulk owing to the effect of the site potential. In this situation, the Fermi surface of the imperfect layer has a strong nesting feature leading to increases in both the antiferromagnetic spin fluctuation and the density of states near the Fermi level, which are in favor of d-wave pairing.