Inhomogeneous multi-carrier superconductivity at LaXO3/SrTiO3 (X=Al or Ti) oxide interfaces

TL;DR

This paper investigates the inhomogeneous superconductivity at LaXO3/SrTiO3 interfaces, revealing a percolative model of superconducting puddles within a metallic matrix and analyzing multi-carrier magneto-transport phenomena.

Contribution

It provides a novel multi-carrier inhomogeneous model explaining superconductivity and the superconductor-to-metal transition at oxide interfaces.

Findings

Superconducting puddles form a percolative network.

Resistance and superfluid density are explained by inhomogeneity.

The superconductor-to-metal transition aligns with magnetic field effects.

Abstract

Several experiments reveal the inhomogeneous character of the superconducting state that occurs when the carrier density of the two-dimensional electron gas formed at the LaXO3/SrTiO3 (X=Al or Ti) interface is tuned above a threshold value by means of gating. Re-analyzing previous measurements, that highlight the presence of two kinds of carriers, with low and high mobility, we shall provide a description of multi-carrier magneto-transport in an inhomogeneous two-dimensional electron gas, gaining insight into the properties of the physics of the systems under investigation. We shall then show that the measured resistance, superfluid density, and tunneling spectra result from the percolative connection of superconducting "puddles" with randomly distributed critical temperatures, embedded in a weakly localizing metallic matrix. We shall also show that this scenario is consistent with the characteristics of the superconductor-to-metal transition driven by a magnetic field. A multi-carrier description of the superconducting state, within a weak-coupling BCS-like model, will be finally discussed.