arXiv: Superconductivity | 2019
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
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.