Thermal fluctuations in ultrasmall intrinsic Josephson junctions

TL;DR

This paper investigates how thermal fluctuations affect the current-voltage behavior of ultrasmall intrinsic Josephson junctions, revealing temperature-dependent switching phenomena and the influence of external circuit impedance.

Contribution

It provides a detailed analysis of thermal phase fluctuations in small Josephson junctions, highlighting the crossover from premature switching to phase diffusion regimes.

Findings

Non-monotonic temperature dependence of switching current

Existence of a hysteretic phase-diffusion branch at crossover temperature

External circuit impedance significantly influences junction behavior

Abstract

Current-voltage curves of small area hysteretic intrinsic Josephson junctions, for which the Josephson energy $E_J=\hbar J_c/2e$ is of order of thermal energy $kT$, are investigated. A non-monotonic temperature dependence of the switching current is observed and explained by thermal phase fluctuations. At low temperatures premature switching from the superconducting into the resistive state is the most important effect of fluctuations. At high temperatures only a single resistive branch is observed. At the cross-over temperature a hysteretic phase-diffusion branch exists. It shows the importance of a frequency-dependent impedance of an external circuit formed by the leads.