In-gap States of Josephson Junction with Two-gap Superconductiors

We investigate the transport property of SIS junctions with two-gap superconductors. The effects of two superconducting condensates on critical current density is estimated by studying the microscopic structure of Josephson current density in a dual-mode tunnel junction with a narrow quasi-classical tunnel barrier. Following the suggestion by Golubov and coworkers [1], we use two Bloch functions to describe the condensates in the two-band superconductors. In this junction, the in-gap states which include the interband interference effect appear at the interfaces due to the discontinuity of the superconducting phase. Also, similar to a Josephson junction [2] involving one-gap and two-gap superconductors, novel broken time-reversal symmetry states are found. We estimate the effects of interband interference and broken time-reversal symmetry on the in-gap bound states and critical Josephson current density. \\[4pt] [1] A. A. Golubov \textit{et al.}, Phys. Rev. Lett. \textbf{103}, 3398 (2009). \\[0pt] [2] T. K. Ng and N. Nagaosa, EPL \textbf{87}, 17003 (2009).