Sommerfeld enhancement factor in two-dimensional Dirac materials

Abstract

In this work the above-band gap absorption spectrum in two-dimensional Dirac materials is calculated with account for the interaction between the photocarriers. Both the screened Rytova-Keldysh and pure Coulomb attraction potentials between the electron and hole are used in the study. We find that, in the materials under consideration, the interaction enhances the absorbance in the narrow interband edge region, in a sharp contrast to the band model with the parabolic free-carrier energy dispersion. We develop an approximation of the weak interaction which allows us to reproduce the main features of the exactly calculated Sommerfeld factor. We show a substantial reduction of this factor at higher frequencies due to the single-particle energy renormalization.

Impurity-band optical transitions in two-dimensional Dirac materials under strain-induced synthetic magnetic field

“…However, because the warping terms are usually small [12], and the intervalley mixing is not sufficient due to the large distance between non-equivalent valleys in the reciprocal space, we neglected their influence on the optical transitions. Third, we have disregarded the possible excitonic effects, the account of which requires a many-body treatment of the problem based on the Bethe-Salpeter equation [15,33]. A careful analysis of excitonic and warpingdependent effects requires non-analytic methods, especially, in the presence of the strain, that is beyond the scope of the present paper.…”