Comparative study of macroscopic quantum tunneling inBi2Sr2CaCu2Oyintrinsic Josephson junctions wi

Abstract

We investigated macroscopic quantum tunneling (MQT) of Bi2Sr2CaCu2Oy intrinsic Josephson junctions (IJJs) for two device structures. One is a small mesa, which is a few nanometers thick with only two or three IJJs, and the other is a stack of a few hundred IJJs in a narrow bridge structure. The experimental results regarding the switching current distribution for the first switch from the zero-voltage state were in good agreement with the conventional theory for a single Josephson junction, indicating that the crossover temperature from thermal activation to the MQT regime for the former device structure was similar to that for the latter device structure. Together with the observation of multiphoton transitions between quantized energy levels in the MQT regime, these results strongly suggest that the observed MQT behavior is intrinsic to a single IJJ in high-Tc cuprates and is independent of the device structure. The switching current distribution for the second switch from the first resistive state, which was carefully distinguished from the first switch, was also compared with respect to the two device structures. In spite of the differences between the heat transfer environments, the second switch exhibited a similar temperature-independent behavior for both devices up to a much higher temperature than the crossover temperature for the first switch. We argue that this cannot be explained in terms of self-heating caused by dissipative currents after the first switch. As possible candidates for this phenomenon, the MQT process for the second switch and the effective increase of the electronic temperature due to the quasiparticle injection are discussed.

Macroscopic quantum tunneling and thermal activation in a small mesa structured Bi2Sr2CaCu2Oyintrinsic Josephson junctions

“…The bias current was slowly ramped up with a constant rate of 1 mA/s. Other details of the experimental setup including the methods to exclude highfrequency noise from the IJJ sample are described elsewhere [4]. Figure 1(a) shows the typical I −V characteristics of a small mesa with only two IJJs (sample M), measured at T = 5 K. The voltage jump for the first switching is about 10 mV, which is larger than the previously reported value for a similar small mesa with 5 IJJs [3].…”

Current distribution of collective thermal depinning of Josephson vortices in naturally stacked Josephson junctions

“…It also gives a false characteristic temperature of crossover from the thermal-activation regime to the macroscopic quantum tunneling regime. 35,36 Thus, to avoid heating, switching current distribution in stacked junctions is usually performed for the switching to the lowest-voltage quasiparticle branch. In the magnetic-field range used this study, however, the JV-flow branches in the low-voltage range are either unidentifiable or unstable to be adopted for studies of the depinning current distribution.…”

Macroscopic quantum tunneling and phase diffusion in a La2−xSrxCuO4Kubo1, Sboychakov2, Nori3 et al. 2012Phys. Rev. B9040View full textAdd to dashboardCite

“…1(b). Unlike typical I-V curves of BSCCO, 1,3,5,7,8,10 no clear multi-branches appear, but all the junctions simultaneously switch to their voltage states. This simultaneous switching event is due to the fact that all the stacked LSCO IJJs are homogeneous, and due to the strong coupling 33 among the IJJs.…”