  Tight-binding models for the recently observed surface electronic bands of
SrTiO3 and KTaO3 are analyzed with a view to bringing out the relevance of
momentum-space chiral angular momentum structures of both orbital and spin
origins. Depending on the strength of electric field associated with inversion
symmetry breaking at the surface, the orbital and the accompanying spin angular
momentum structures reveal complex linear and cubic dependencies in the
momentum k (linear and cubic Rashba effects, respectively) in a band-specific
manner. Analytical expressions for the cubic orbital and spin Rashba effects
are derived by way of unitary transformation technique we developed, and
compared to numerical calculations. Due to the C4v symmetry of the perovskite
structure the cubic Rashba effect appears as in-plane modulations.

Materials Science