Fermi-edge singularities in the optical absorption and emission of doped indirect quantum wires

Fermi-edge singularities in the optical spectra of doped indirect quantum wires are theoretically analyzed by using a screened Coulomb interaction. In the extreme quantum limit in which the Fermi level lies in the lowest electron subband, strong singularities appear when three requisites are fulfilled: (i) infinite hole mass, (ii) Fermi energy slightly smaller than the intersubband spacing for electrons, and (iii) a transverse separation of the order of 100 nm exists between the electron and the hole. In such a case the optical singularity associated with the bottom of the electron subband is negligible with respect to the one at the Fermi level. These results allow a clarifying discussion on the available experimental information.