SWITCHING DYNAMICS IN STRONGLY COUPLED JOSEPHSON JUNCTIONS

Recently, quantum dynamics and coherence in Josephson junctions (JJs) made of high Tc superconductors (HTSCs) attract much attention. The HTSCs have relatively large energy gap and higher plasma frequency compared to those of metal superconductors, which suggests their high potential for quantum electron devices. On the other hand, the HTSC JJs have a disadvantage that the pairing symmetry is d-wave, and thus the intrinsic damping effect in the dynamic due to the nodal quasiparticles is inevitable. In addition to this, the coupling effect due to the atomic scale stack structure induces complex switching. Therefore, the peculiarities in quantum dynamics of the HTSC JJs must be clarified in order to realize the HTSCs quantum electronics. Here we report our efforts to observe macroscopic quantum tunneling and quantum coherence in the HTSC JJs.