Spin-polarized electronic states and atomic reconstructions at antiperovskite Sr3SnO(001) polar surfaces

Abstract

We report a first-principles investigation of the atomic and electronic properties at the perfect and defective (001) surfaces of the antiperovskite ${\mathrm{Sr}}_{3}\mathrm{Sn}\mathrm{O}$. We first performed a thermodynamical study of the atomic structure terminations and demonstrated that SrSn-terminated surfaces should be the most stable one, either with a perfect $(1\ifmmode\times\else\texttimes\fi{}1$) structure or with a $(2\ifmmode\times\else\texttimes\fi{}1)$ reconstruction induced by the formation of Sn vacancies. We detailed the surface gap states obtained for these surfaces, which we compare with those of other surface terminations, also having relatively low energies. These gap states, located near the Fermi level, could have a major contribution to the transport properties. Due to the lack of inversion symmetry associated with the surface, we predict that they also experience spin splittings, an important property for spin-orbitronic applications. Finally, we found that ${\mathrm{Sr}}_{2}\mathrm{O}$-terminated surfaces could display a ferromagnetic ordering resulting from the population of $4d$ orbitals of Sr atoms at the surface and that this could lead to the formation of a spin-polarized two-dimensional electron gas.