We experimentally investigate charge transport in In-CrSb and In-CrSb-In proximity devices, which are formed as junctions between superconducting indium leads and thick single crystal flakes of altermagnet CrSb. For double In-CrSb-In junctions, dV/dI(B) curves are mirrored in respect to zero field for two magnetic field sweep directions, which is characteristic behavior of a Josephson spin valve. Also, we demonstrate Josephson diode effect by direct measurement of the critical current for two opposite directions in external magnetic field. We interpret these observations as a joint effect of the spin-polarized topological surface states and the altermagnetic spin splitting of the bulk bands in CrSb. For a single In-CrSb interface, the superconducting gap oscillates in magnetic field for both field orientations, which strongly resembles the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) behavior. FFLO is based on finite-momentum Cooper pairing, therefore, it is fully compatible with the requirements for the Josephson diode effect.
@article{arxiv.2602.08766,
title = {Josephson diode and spin-valve effects on the surface of altermagnet CrSb},
author = {V. D. Esin and D. Yu. Kazmin and Yu. S. Barash and A. V. Timonina and N. N. Kolesnikov and E. V. Deviatov},
journal= {arXiv preprint arXiv:2602.08766},
year = {2026}
}