Resonant tunneling of fluctuation Cooper pairs

TL;DR

This paper reports sharp current spikes caused by resonant tunneling of fluctuation Cooper pairs near the superconducting transition temperature, providing a new method to measure fluctuation dynamics.

Contribution

It introduces a novel phenomenon of radiation-induced resonant tunneling of fluctuation Cooper pairs, enabling direct measurement of their lifetime near Tc.

Findings

Current spikes grow sharper near Tc

Resonant tunneling reveals fluctuation Cooper pair lifetime

Challenges conventional view of fluctuations as smoothing phenomena

Abstract

Superconducting fluctuations have proved to be an irreplaceable source of information about microscopic and macroscopic material parameters that could be inferred from the experiment. According to common wisdom, the effect of thermodynamic fluctuations in the vicinity of the superconducting transition temperature, Tc, is to round off all of the sharp corners and discontinuities, which otherwise would have been expected to occur at Tc. Here we report the current spikes due to radiation-induced resonant tunneling of fluctuation Cooper pairs between two superconductors which grow even sharper and more pronounced upon approach to Tc. This striking effect offers an unprecedented tool for direct measurements of fluctuation Cooper pairs' lifetime, which is key to our understanding of the fluctuation regime. Our finding marks a radical departure from the conventional view of superconducting fluctuations as blurring and rounding phenomenon.