Majoranas with a twist: tunable Majorana zero modes in altermagnetic heterostructures

One of the most promising experimental setups for realising Majorana zero modes (MZMs) involves a 1D semiconductor-superconductor heterostructure subjected to a Zeeman field. However, a significant challenge is that the magnetic field suppresses the superconducting gap. Recent work by Ghorashi et al. proposed replacing the Zeeman field by proximity to an altermagnet, a newly discovered phase of collinear magnetism hosting spin-split band structures with zero net magnetization, thus circumventing this issue. In this talk, we provide a microscopic derivation of the model proposed in the aforementioned work and demonstrate that rotating the wire provides a tuning knob for going in and out of the topological phase. For d-wave, g-wave and i-wave altermagnetic pairing, we derive angle-dependent topological gap-closing conditions and show, both by symmetry considerations and by explicit calculation, that the altermagnetic response vanishes if the wire is placed on a nodal line of the altermagnet. Our results provide general predictions independent of any particular material realization and introduce wire rotation as a novel tunable parameter for the emergence of MZMs.