Polarization selection rules in photoemission from the valence bands of zinc-blende-structure semiconductors.

Abstract

Bulk valence-band transitions in angle-resolved photoemission spectra depend on the polarization of the incident light. The suppression or enhancement of direct transitions results from symmetry enforced selection rules in the photoexcitation process. Photoemission involves a transition from an initial valence band to a final-state band via the electric dipole perturbation describing the photon. This paper focuses on the symmetries of the initial states, the photon operators, and the final states. The final-state band symmetries are deduced from free-electron-like bands. Applying symmetry arguments to the photon matrix element, we infer important selection rules for different polarization geometries of the photon field. We apply the concept to normal emission valence-band spectra of the split-off band in CdTe(100), showing that the transition along the \ensuremath{\Delta} line is the dominant emission feature for p polarization while it is completely suppressed using s-polarized light.