$d_{xz\mathrm{/}yz}$ Orbital Subband Structures and Chiral Orbital Angular Momentum in the (001) Surface States of SrTiO${}_3$

We have performed angle resolved photoemission spectroscopy (ARPES) experiments on the surface states of SrTiO${}_3$(001) using linearly and circularly polarized light to investigate the subband structures of out-of-plane $d_{xz\mathrm{/}yz}$ orbitals and chiral orbital angular momentum (OAM). The data taken in the first Brillouin zone reveal new subbands for $d_{xz\mathrm{/}yz}$ orbitals with Fermi wave vectors of 0.25 and 0.45 ${\mathring{\mathrm{A}}}^{-1}$ in addition to the previously reported ones. As a result, there are at least two subbands for all the Ti 3d t${}_{2g}$ orbitals. Our circular dichroism ARPES data is suggestive of a chiral OAM structure in the surface states and may provide clues to the origin of the linear Rashba-like surface band splitting.