Tunneling Spectroscopy Across the Superconductor-Insulator Thermal Transition

TL;DR

This paper uses Monte Carlo simulations to explore how superconducting regions persist and fragment in disordered superconductors across thermal transitions, revealing multiple temperature scales for superconductivity and pseudogap phenomena.

Contribution

It introduces a spatially resolved Monte Carlo approach to analyze the superconductor-insulator transition and identifies multiple distinct temperature scales for superconducting and pseudogap states.

Findings

Superconducting nanoregions survive above the bulk transition temperature.

Superconducting regions fragment into small clusters at high temperatures.

The pseudogap persists to a separate, higher temperature scale.

Abstract

Advances in scanning tunneling spectroscopy reveal the presence of superconducting nanoregions well past the bulk thermal transition in strongly disordered superconductors. We use a Monte Carlo tool to capture the spatially differentiated amplitude and phase fluctuations in such a material and establish spatial maps of the coherence peak as the superconductor is driven through the thermal transition. Analysis of the local density of states reveals that superconducting regions shrink and fragment with increasing temperature, but survive in small clusters to a temperature $T_{clust} >> T_{c}$ . The gap (or pseudogap) in the spectrum survives in general to another independent scale, $T_{g}$, depending on the strength of interaction. This multiple scale description is consistent with recent measurements and defines the framework for analysing strongly disordered superconductors.