Electrostatically tuned quantum superconductor-metal-insulator transition at the LaAlO3/SrTiO3 interface

TL;DR

This study investigates the electric field-tuned superconductor-metal-insulator transition at the LaAlO3/SrTiO3 interface, revealing a BKT transition line ending at a metallic quantum critical point and classifying the quantum phase transition within the 3D-xy universality class.

Contribution

It provides a detailed finite size scaling analysis demonstrating the compatibility of the phase transition with BKT behavior and identifies the universality class of the quantum phase transition.

Findings

Confirmation of BKT critical line ending at a metallic quantum critical point.

Critical exponents z=1 and nu=0.66 suggest 3D-xy universality class.

Existence of a gate voltage dependent limiting length in the intermediate regime.

Abstract

Recently superconductivity at the interface between the insulators LaAlO3 and SrTiO3 has been tuned with the electric field effect to an unprecedented range of transition temperatures. Here we perform a detailed finite size scaling analysis to explore the compatibility of the phase transition line with Berezinskii-Kosterlitz-Thouless (BKT) behavior and a 2D-quantum phase(QP)-transition. In an intermediate regime, limited by a gate voltage dependent limiting length, we uncover remarkable consistency with a BKT-critical line ending at a metallic quantum critical point, separating a weakly localized insulator from the superconducting phase. Our estimates for the critical exponents of the 2D-QP-transition, z=1 and nu=0.66, suggest that it belongs to the 3D-xy universality class.