Tunable Josephson diode effect in singlet superconductor-altermagnet-triplet superconductor junctions

Abstract: Recently discovered phase of collinear magnet called, altermagnet breaks time reversal symmetry (TRS), exhibits momentum-dependent spin-splitting of band structure with zero net magnetization. In this work, we theoretically investigate the Josephson junction (JJ) of spin singlet superconductor (SC)/altermagnet/spin triplet SC and demonstrate that it manifests field free Josephson diode effect (JDE). We illustrate that there are four key requisites to have JDE in such JJs, namely, broken TRS, left and right SC in the JJ shall be non-identical, presence of spin orbit interaction, and anisotropy in spin polarization at the Fermi surface or anisotropy in pair potential of the SC. It has also been shown that by applying a gate potential in the altermagnetic regime, one can not only reverse the sign of efficiency but also modulate its magnitude. Our system can be used as a superconducting rectifier that can be tuned efficiently using gate voltage and system parameters without having external magnetic field.