Large spin splittings due to the orbital degree of freedom and spin textures in a ferroelectric nitride perovskite

摘要

First-principles simulations are conducted to predict that ferroelectric nitride perovskite LaWN3 not only exhibits large spin splittings (2.7 eV angstrom) but also possesses unique spin textures for some of its conduction levels. Such spin splittings around the Gamma and L points cannot be interpreted as a typical mixture of Rashba or Dresselhaus configurations but rather require the development of four-band k center dot p models with high-order terms. We further identify that, for some bands, spin splittings can be greatly contributed by the pure orbital degree of freedom (PODF), a unique character of our four-band Hamiltonian compared to the traditional two-band version. The concept of PODF-enhanced spin splittings paves a way for designing materials with large spin splittings. Moreover, the energy levels possessing such large splittings and complex spin textures can be brought close to the conduction-band minimum by applying epitaxial strain.