Comparative Study of First and Second Switches with Nearly Identical Switching Current in Bi$_2$Sr$_2$Ca$_{0.85}$Y$_{0.15}$Cu$_2$O$_y$ Intrinsic Josephson Junctions

TL;DR

This study compares the first and second switching currents in Bi2212 intrinsic Josephson junctions, revealing that their crossover temperatures align and suggesting nonlinear bifurcation phenomena influence escape dynamics.

Contribution

It provides new insights into the similarity of switching behaviors and phase escape mechanisms in IJJs, especially regarding the crossover temperature and nonlinear effects.

Findings

Crossover temperature for second switch is reduced to ~2.8 K, matching the first switch.

Anomalous enhancement of crossover temperature is linked to the phase running state.

Evidence of nonlinear bifurcation phenomena in microwave-induced escape processes.

Abstract

We present a study of the first and second switches (SWs) with nearly identical switching current $I_{\rm SW}$ in Bi$_2$Sr$_2$Ca$_{0.85}$Y$_{0.15}$Cu$_2$O$_y$ intrinsic Josephson junctions (IJJs). In contrast to early studies where a large difference between $I_{\rm SW}^{\rm 1st}$ and $I_{\rm SW}^{\rm 2nd}$ was observed, a crossover temperature $T_{\rm cr}$ to the quantum phase escapes for the 2nd SW is strongly reduced $(\sim$2.8~K) and agrees with that for the 1st SW. This confirms that the anomalous enhancement of $T_{\rm cr}^{\rm 2nd}$, commonly observed in the IJJs with $I_{\rm SW}^{\rm 1st} < I_{\rm SW}^{\rm 2nd}$, originates from the phase running state after the 1st SW. Detailed analysis of the microwave-induced escapes strongly suggests that nonlinear bifurcated phenomena possibly occurs in IJJs.