Interplay of intra- and interband absorption in a disordered graphene

TL;DR

This paper investigates how intra- and interband absorption processes in disordered graphene affect its THz and MIR spectral response, revealing the roles of different disorder types and matching experimental data.

Contribution

It provides a detailed analysis of intra- and interband absorption interplay in disordered graphene, linking disorder characteristics to spectral features and experimental observations.

Findings

Interband absorption edge smearing is caused by long-range disorder.

Intraband absorption is influenced by finite-range scattering.

Theoretical results align well with experimental data.

Abstract

The absorption of heavily doped graphene in the terahertz (THz) and mid-infrared (MIR) spectral regions is considered taking into account both the elastic scattering due to finite-range disorder and the variations of concentration due to long-range disorder. Interplay between intra- and interband transitions is analyzed for the high-frequency regime of response, near the Pauli blocking threshold. The gate voltage and temperature dependencies of the absorption efficiency are calculated. It is demonstrated that for typical parameters, the smearing of the interband absorption edge is determined by a unscreened part of long-range disorder while the intraband absorption is determined by finite-range scattering. The latter yields the spectral dependencies which deviate from those following from the Drude formula. The obtained dependencies are in good agreement with recent experimental results. The comparison of the results of our calculations with the experimental data provides a possibility to extract the disorder characteristics.