Josephson diode effect in altermagnet-based s-wave superconductor junction

We investigate the possible Josephson diode effect (JDE) in a two-dimensional (2D) nonmagnetic planar s-wave superconductor junction, which is constructed on a spin-collinear d-wave altermagnet (AM) material in the presence of Rashba spin–orbit interaction. It is demonstrated that the JDE is critically dependent on the crystalline axis of the AM relative to the current direction. The d_x²–y² magnetization symmetry can support a JDE whereas the d_xy symmetry does not facilitate it. The JDE efficiency can reach up to 40% and can be adjusted by an additional asymmetric gate voltage applied to the non-superconducting region of the junction, including control of its polarity. Our findings provide an electrical means to control the JDE within a non-magnetic AM-based superconducting junction.