Combined Angle-Resolved Photoemission Spectroscopy and Theoretical Study of the Surface Electronic Structure of SrTiO$_{3}$

The surface electronic structure of the O 2$p$-derived valence band states of (001)-oriented, TiO$_{2}$-terminated SrTiO$_{3}$ is measured along various crystallographic directions using angle-resolved photoemission spectroscopy (ARPES). A comparison of ARPES spectra to \textit{ab initio}, density functional theory (DFT) band structure calculations as well as the theoretical band structure calculated at the tight binding level are in excellent agreement. ARPES measurements also reveal a mid-gap state located roughly 0.5 eV above the valence band which we interpret as a surface state. This interpretation is supported by DFT calculations of an SrTiO$_{3}$ slab which reveals the existence of a surface state located in the gap roughly 0.5 eV above the projected valence band.