Using Annular Josephson Tunnel Junctions to Monitor Causal Horizon

TL;DR

This paper demonstrates how annular Josephson Tunnel Junctions can be used to measure causal horizons during phase transitions by analyzing flux trapping probabilities as a function of quench time.

Contribution

It introduces a method to trace causal horizons through flux production measurements in Josephson junctions during rapid phase transitions.

Findings

Flux trapping probability follows a power-law dependence on quench time.

The scaling exponent for flux trapping is approximately 0.25.

Experimental results agree with theoretical predictions.

Abstract

If systems change as fast as possible as they pass through a phase transition then the initial domain structure is constrained by causality. We shall show how we can trace these causal horizons by measuring the spontaneous production of flux in annular Josephson Tunnel Junctions as a function of the quench time $\tau_{Q}$ into the superconducting phase. A specific test of our analysis is that the probability P$_{1}$ to trap a single fluxon at the N-S transition clearly follows an allometric dependence on $\tau_{Q}$ as $P_1 = a \tau_Q^{-\sigma}$, with a scaling exponent $\sigma = 0.25$, in agreement with the data.