Temperature-Dependent Electroabsorption on the Indirect Edge of Trigonal Selenium

Electroabsorption was measured on selenium single crystals as a function of temperature, polarization of light, and direction of the modulating electric field. Interpretation along the lines of Elliot's theory of indirect excitonic transitions yields the assignment of the conduction-band minimum to the point Z=(0, 0, 1)πc of the Brillouin zone or its close neighborhood. The assignment of the maximum of the valence band to the point H=(4/3πa, 0, πc) is reinforced by the reported measurements.