Multi-band superconductivity and nanoscale inhomogeneity at oxide interfaces

TL;DR

This paper investigates the inhomogeneous nature of superconductivity at oxide interfaces, modeling it as a percolative system of superconducting puddles with multi-band characteristics, and correlates microscopic parameters with experimental data.

Contribution

It introduces a multi-band BCS model to describe intra-puddle superconductivity and links microscopic parameters to observed inhomogeneity and critical temperature variations.

Findings

Superconductivity arises from filamentary puddles with varying critical temperatures.

A percolative model accurately fits transport data and explains superfluid density.

Microscopic parameters are consistent with the dependence of critical temperature on carrier density.

Abstract

The two-dimensional electron gas at the LaTiO3/SrTiO3 or LaAlO3/SrTiO3 oxide interfaces becomes superconducting when the carrier density is tuned by gating. The measured resistance and superfluid density reveal an inhomogeneous superconductivity resulting from percolation of filamentary structures of superconducting "puddles" with randomly distributed critical temperatures, embedded in a non-superconducting matrix. Following the evidence that superconductivity is related to the appearance of high-mobility carriers, we model intra-puddle superconductivity by a multi-band system within a weak coupling BCS scheme. The microscopic parameters, extracted by fitting the transport data with a percolative model, yield a consistent description of the dependence of the average intra-puddle critical temperature and superfluid density on the carrier density.