Speaker
Description
We present a unified theoretical study of superconducting films and heterostructures hosting collinear $d$-wave altermagnetic order. Using a Ginzburg-Landau description, we show that the interplay between superconductivity and altermagnetism produces characteristic fourfold anisotropies in the critical temperature, parallel critical field, and critical current density under external magnetic fields and in-plane supercurrents. We further demonstrate that, in the vortex state, altermagnetism transforms conventional circular Abrikosov vortices into elliptical ones, with their orientation controlled by the sign of the magnetic-field component parallel to the Néel vector. As a consequence, superconducting films with pinning defects or geometrical constraints can exhibit nonreciprocal magnetization curves arising from different vortex-vortex interaction energies for opposite field orientations. These effects originate from an altermagnetism-induced effective-mass anisotropy generated by the coupling between the external field and the Néel vector. Together, these results identify a broad set of experimentally accessible superconducting signatures of altermagnetism, relevant both to intrinsic altermagnetic superconductors and to superconductor/altermagnet hybrid structures.