First-principles design of superconductor–semiconductor heterostructures for topological superconductivity

Over the past decade, semiconductor–superconductor (SM–SC) heterostructures have emerged as promising platforms for realizing topological superconductivity and hosting Majorana zero modes. However, most experimental efforts have focused on low-Tc ​ conventional superconductors such as Aluminum, which limit the accessible temperature and energy scales. Here, we propose a planar hybrid system composed of a monolayer of iron selenide (FeSe) interfaced with gallium arsenide (GaAs), forming a high-Tc SM–SC heterostructure. The FeSe monolayer, reported to superconduct with a large gap of 10–15 meV, can provide a strong proximity effect and enhanced robustness against thermal decoherence. Using first-principles computations, we investigate the electronic structure of FeSe/GaAs and demonstrate conditions that optimize superconducting proximity coupling. From maximally localized Wannier functions, we construct an effective low-energy Hamiltonian to map the topological phase diagram, revealing regimes where the system supports nontrivial topological states.