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arXiv · 1412.5276

Two-dimensional macroscopic quantum tunneling in multi-gap superconductor Josephson junctions

Hidehiro Asai·Shiro Kawabata·Yukihiro Ota·Masahiko Machida
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Abstract

Low-temperature characters of superconducting devices yield definite probes for different superconducting phenomena. We study the macroscopic quantum tunneling (MQT) in a Josephson junction, composed of a single-gap superconductor and a two-gap superconductor. Since this junction has two kinds to the superconducting phase differences, calculating the MQT escape rate requires the analysis of quantum tunneling in a multi-dimensional configuration space. Our approach is the semi-classical approximation along a 1D curve in a 2D potential- energy landscape, connecting two adjacent potential (local) minimums through a saddle point. We find that this system has two plausible tunneling paths; an in-phase path and an out-of-phase path. The former is characterized by the Josephson-plasma frequency, whereas the latter is by the frequency of the characteristic collective mode in a two-band superconductor, Josephson- Leggett mode. Depending on external bias current and inter-band Josephson-coupling energy, one of them mainly contributes to the MQT. Our numerical calculations show that the difference between the in-phase path and the out-of-phase path is manifest, with respect to the bias- current-dependence of the MQT escape rate. This result suggests that our MQT setting be an indicator of the Josephson-Leggett mode.

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Hidehiro Asai, Shiro Kawabata, Yukihiro Ota, Masahiko Machida. 2014-12-17. Two-dimensional macroscopic quantum tunneling in multi-gap superconductor Josephson junctions. https://doi.org/10.1088/1742-6596%2F568%2F2%2F022006

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