Indirect Exciton Dispersion and Line Shape in Ge

Abstract

The effective-mass equation for indirect excitons in Ge is solved taking the degeneracy and anisotropy of the bands into account. The calculated binding energies of the anisotropy split ground state (4.18 and 3.17 meV) are in excellent agreement with experiment (4.15 and 3.14 meV). The method is then extended to calculate the energy-momentum dispersion of excitons, which are strongly nonparabolic, and account well, with no adjustable parameters, for the recently measured modulated absorption line shape.