Multipolar order and piezo-response in altermagnets

Altermagnets host magnetic multipoles, which can be seen in their reciprocal space spin-splittings, real-space spin densities, or nontrivial Berry curvature patterns. The effect of these multipoles is also evident in the form of many response tensors, such as spin Hall or piezomagnetism which have been studied in detail. In this talk, I am going to discuss our recent first principles and tight binding results on various altermagnets, focusing on their macroscopic response to strain and magnetic fields using a symmetry-guided approach. In particular, I will show the change in magnetic multipoles under the effect of external fields, and explain their dependence (or lack thereof) on spin-orbit coupling. Finally, I will conclude by a discussion of the hidden signatures of magnetic multipoles that go beyond the simple observables.