Correlated non-Gaussian phase fluctuations in LaAlO3/SrTiO3 heterointerfaces

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 LaAlO3/SrTiO3 heterostructures. The non-Gaussian fluctuations appear between the Berezinskii-Kosterlitz-Thouless transition temperature TBKT and the mean-field transition temperature TC. 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.