Nonlinear Superconducting Magnetoelectric Effect.

Supercurrent flow can induce a nonvanishing spin magnetization in noncentrosymmetric superconductors with spin-orbit interaction. Often known as the nondissipative magnetoelectric effect, these are most commonly found at linear order in supercurrent flow. Here, we propose that a nonlinear superconducting magnetoelectric (NSM) effect can naturally manifest in magnet-superconductor heterostructures. In such platforms, NSM manifests as the spin polarization generated as a second-order response to a driving supercurrent. Strikingly, we find NSM survives centrosymmetry and is the leading-order magnetic response in a variety of magnetic materials that include both collinear magnets (e.g., d-wave planar altermagnet thin film-superconductor) as well as noncollinear magnets (e.g., kagome-superconductor systems). This renders NSM a powerful electric and nondissipative means of controlling magnetization in magnet-superconductor heterostructures, a promising platform for superconducting spintronics.