Frenkel excitons and band structure in Sb2S3 single crystals

Anisotropy of optical properties of Sb2S3 single crystals was investigated at 11 and 300 K. Ground and excited states of four excitonic states (A, B, C and D) were found out. Parameters of observed excitons and bands V-1 - V-4 were determined. In Gamma point of Brillouin zone the effective masses of electrons in the bottom conduction band (m(c)* = 1.08m(0)) and of holes in four top valence bands (m(v1)*, m(v2)* = 2.91m(0) and m(v3)*, m(v4)* = 3.12m(0)) were estimated. The splitting magnitudes of valence bands V-1 - V-2 in the Brillouin zone center by crystal field (Delta(cf) = 20 meV) and by spin-orbital interaction (Delta(so) = 375 meV) were calculated. V-3 and V-4 bands have splitting of 198 meV. The observed features were interpreted on the base of existing theoretically calculated band structure and symmetries of excitons in G point of Brillouin zone for single crystals of orthorhombic symmetry (Pnma).