Band-to-band transitions and free exciton states in low-symmetry crystalline GaTe

Abstract

In this paper we derived the selection rules for band-to-band transitions in low-symmetry crystalline GaTe and explained the low-temperature (2 K) absorption spectra at two different polarization configurations for this material. It is found that the top two valence bands of crystalline GaTe at the high symmetry Γ-point have one-dimensional degeneracy and are weakly separated (<0.5 meV). From this band structure, we re-analyzed the free exciton states in crystalline GaTe and found that the X 1 peak is composed of the heavy-hole (HH) and light-hole (LH) singlet excitons, while the X 2 peak is composed of the HH and LH triplet excitons.