Correlated Non-Gaussian phase fluctuations in LaAlO$_3$/SrTiO$_3$ heterointerface

TL;DR

This study investigates large non-Gaussian phase fluctuations near the superconducting transition in LaAlO₃/SrTiO₃ heterostructures, revealing their origin and confirming the two-dimensional nature of superconductivity.

Contribution

It demonstrates that non-Gaussian fluctuations are due to percolative Josephson network transitions and introduces a new method to study BKT transitions in 2D inhomogeneous superconductors.

Findings

Non-Gaussian fluctuations occur between T_BKT and T_C.

Fluctuations are mainly due to percolative Josephson network transition.

Superconductivity is confirmed to be two-dimensional.

Abstract

We probe the existence of large correlated non-Gaussian phase fluctuations in the vicinity of the superconducting phase transition in the conducting layer residing at the interface of LaAlO$_3$/SrTiO$_3$ heterostructures. The non-Gaussian fluctuations appear between the Berezinskii-Kosterlitz-Thouless transition temperature $T_{BKT}$ and the mean field transition temperature $T_C$. Subsequent theoretical analysis reveals that non-Gaussianity arises predominantly due to the percolative transition of a Josephson coupled network of superconductors. Our results confirm that the superconductivity in this system is confined to two-dimensions. Our study of the non-Gaussian resistance fluctuation spectrum provides a novel means to explore the BKT-transition in two-dimensional inhomogeneous superconductors.