On the pseudospin description of the electron Bloch bands

Abstract

We study the transformation properties of the electron states in crystals with spin–orbit coupling, focusing primarily on the limitations of the frequently used pseudospin-1∕2 description of twofold degenerate Bloch bands. Using the language of corepresentations of magnetic point groups, we construct the Bloch bases across the Brillouin zone in a way which is consistent with all symmetry requirements. This construction is applied to derive the effective spin–orbit Hamiltonians in noncentrosymmetric crystals, known as the generalized Rashba models, in both single-band and multiband cases.