Stability of thermally bistable states and their switching in superconducting weak link

TL;DR

This study investigates the stability and switching behavior of superconducting weak links acting as Josephson junctions, focusing on thermal fluctuations and metastable states to improve single-photon detector performance.

Contribution

The paper provides an experimental analysis of switching statistics and introduces a thermal double-well model to understand state stability in superconducting weak links.

Findings

Measured lifetimes of metastable states near hysteresis crossover.

Observed telegraphic noise indicating random state switching.

Thermal fluctuations significantly influence state stability.

Abstract

Superconducting weak link (WL), acting as a Josephson junction (JJ), is one of the widely used elements in superconductor science and quantum circuits. A hysteretic JJ with robust switching between its superconducting and resistive state is an excellent candidate for single-photon detection. However, the ubiquitous fluctuations in the junction strongly influence the stability of the states and, thus, the transition from one to the other. Here, we present an experimental study of switching statistics of critical and retrapping currents of a JJ based on niobium WL in its hysteretic regime. The mean lifetimes of the two metastable states, namely, the zero-voltage superconducting state and finite-voltage resistive state, are estimated from the distributions. Further, close to the hysteresis crossover temperature, observed telegraphic noise in the time domain due to random switching between the states provides their lifetimes directly. We present a thermal model introducing a double-well (bistable) feature with an intriguing quantity with respect to the devices' temperature states. The effects of temperature fluctuations on the stability of the states are shown. We discuss our results toward further improvement of the efficiency of superconducting WL or nanowire single-photon detectors.