Sommerfeld enhancement factor in two-dimensional Dirac materials

TL;DR

This paper investigates how electron-hole interactions affect the optical absorption spectrum in two-dimensional Dirac materials, revealing an enhancement near the band edge and a reduction at higher frequencies.

Contribution

It introduces a model for the Sommerfeld enhancement factor in 2D Dirac materials considering both screened and pure Coulomb potentials, with an approximation for weak interactions.

Findings

Interaction enhances absorbance near the interband edge

Weak interaction approximation reproduces main features of the Sommerfeld factor

Reduction of the enhancement factor at higher frequencies due to energy renormalization

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.