Macroscopic quantum tunneling and phase diffusion in a La$_{2-x}$Sr$_x$CuO$_4$ intrinsic Josephson junction stack

TL;DR

This study investigates macroscopic quantum tunneling and phase diffusion in a La$_{2-x}$Sr$_x$CuO$_4$ intrinsic Josephson junction stack, revealing a crossover from thermal to quantum escape mechanisms around 2 K.

Contribution

It provides experimental evidence of macroscopic quantum tunneling in LSCO IJJ stacks and applies a theoretical model accounting for dissipation and phase re-trapping effects.

Findings

Escape rate saturates below 2 K, indicating quantum tunneling dominance.

Theoretical model aligns well with experimental data across temperature regimes.

Crossover temperature for quantum effects is approximately 2 K.

Abstract

We performed measurements of switching current distribution in a submicron La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) intrinsic Josephson junction (IJJ) stack in a wide temperature range. The escape rate saturates below approximately 2\,K, indicating that the escape event is dominated by a macroscopic quantum tunneling (MQT) process with a crossover temperature $T^{*}\approx2\,$K. We applied the theory of MQT for IJJ stacks, taking into account dissipation and the phase re-trapping effect in the LSCO IJJ stack. The theory is in good agreement with the experiment both in the MQT and in the thermal activation regimes.