Electrically switchable hidden spin polarization in antiferroelectric crystals

Hidden spin polarization (HSP) emerges in centrosymmetric crystals where visible spin splittings in the real space can be observed because of the lack of inversion symmetry in each local sector. Starting from tight-binding models, we introduce nonsymmorphic antiferroelectric (AFE) crystals as a new class of functional materials that can exhibit strong local spin polarization. Such AFE crystals can be basically classified as in-plane and out-of-plane AFE configurations, and can be reversibly switched to the ferroelectric phase by an electric field to manifest global spin splittings, enabling a nonvolatile electrical control of spin-dependent properties. Based on first-principle calculations, we predict the realization of strong HSP in the AFE phase of a newly-discovered two-dimensional materials, quintuple-layer (QL) LiBiO$_2$. Furthermore, the spontaneous electric polarization ($\sim$ 0.3 nC/m) and the transition barrier as well as the tunable spin polarization of QL-LiBiO$_2$ are discussed.