Universal scaling of the order-parameter distribution in strongly disordered superconductors

TL;DR

This paper reveals a universal scaling law for the distribution of the superconducting order parameter near the superconductor-insulator transition, supported by both theoretical models and experimental STM data in disordered NbN samples.

Contribution

It introduces a universal rescaling of the order-parameter distribution applicable to disordered superconductors, bridging theory and experiment.

Findings

Universal rescaling of OPD identified in models and experiments

Excellent agreement between theoretical predictions and STM data

Advances understanding of the superconductor-insulator transition

Abstract

We investigate theoretically and experimentally the statistical properties of the inhomogeneous order-parameter distribution (OPD) at the verge of the superconductor-insulator transition (SIT). We find within two prototype fermionic and bosonic models for disordered superconductors that one can identify a universal rescaling of the OPD. By performing scanning-tunneling microscopy experiments in three samples of NbN with increasing disorder we show that such a rescaling describes also with an excellent accuracy the experimental data. These results can provide a breakthrough in our understanding of the SIT.