Enhancement of the superconducting transition temperature in La2-xSrxCuO4 bilayers: Role of pairing and phase stiffness

TL;DR

This study demonstrates that bilayer structures of underdoped and overdoped La2-xSrxCuO4 can significantly increase the superconducting transition temperature, highlighting the importance of interface effects, pairing strength, and phase stiffness in high-Tc superconductivity.

Contribution

It reveals that interface engineering in La2-xSrxCuO4 bilayers enhances Tc by combining high pairing scale and increased phase stiffness, a novel approach in superconductor design.

Findings

Tc exceeds that of optimally-doped films near 1/8 doping

Superconductivity enhancement is confined to the interface

High pairing scale and phase stiffness are key factors

Abstract

The superconducting transition temperature, Tc, of bilayers comprising underdoped La2-xSrxCuO4 films capped by a thin heavily overdoped metallic La1.65Sr0.35CuO4 layer, is found to increase with respect to Tc of the bare underdoped films. The highest Tc is achieved for x = 0.12, close to the 'anomalous' 1/8 doping level, and exceeds that of the optimally-doped bare film. Our data suggest that the enhanced superconductivity is confined to the interface between the layers. We attribute the effect to a combination of the high pairing scale in the underdoped layer with an enhanced phase stiffness induced by the overdoped film.