Josephson diode effect via a nonequilibrium Rashba system

Mori, Michiyasu  ; Koshibae, Wataru*; Maekawa, Sadamichi*

Josephson diode effect between two singlet superconductors separated by the Rashba system is studied theoretically. The coupling energy of two superconductors is analytically calculated using a tunneling Hamiltonian with a one-dimensional model. In a magnetic field perpendicular to an applied current, we obtain a coupling energy proportional to the applied current and magnetic field. This makes the critical current asymmetric with respect to the current or the magnetic field, i.e., Josephson diode effect. More importantly, depending on a distance between the superconducting electrodes , the Josephson diode effect changes its magnitude and sign. The magnitude is inversely proportional to a band split caused by the spin-orbit interaction. Since is experimentally controllable, the Josephson diode effect can be optimized by tuning of .