Chiral orbital angular momentum perspective on surface electronic states of SrTiO3 and KTaO3

Tight-binding models suitable for the recently observed surface electronic bands of $\rm{SrTiO_3}$ and $\rm{KTaO_3}$ are analyzed with a view to bringing out the relevance of chiral orbital angular momentum (OAM) structure in the $t_{2g}$-derived bands. With the inversion symmetry breaking at the surface, orbital chiralities of the three bands (neglecting spin splitting) are $m = +1,0,-1$. Further inclusion of spin-orbit interaction induces linear Rashba splitting on the chiral OAM bands, but not in the non-chiral, $m=0$ band structure. Our predictions can be easily verified by circular dichroism ARPES experiment.