Excitonic terahertz absorption in semiconductors with effective-mass anisotropies

TL;DR

This paper develops a microscopic method to analyze excitonic properties and terahertz absorption in anisotropic semiconductors, demonstrating how effective mass anisotropy influences absorption resonances, exemplified by germanium.

Contribution

It introduces a new microscopic approach for calculating excitonic and terahertz responses in anisotropic semiconductors, highlighting the impact of effective mass anisotropy.

Findings

Germanium exhibits two distinct terahertz absorption resonances due to anisotropic electron mass.

The anisotropic effective mass causes a separation of 0.8 meV between absorption peaks.

The approach can be applied to other anisotropic semiconductor materials.

Abstract

A microscopic approach is developed to compute the excitonic properties and the corresponding terahertz response for semiconductors characterized by anisotropic effective masses. The approach is illustrated for the example of germanium where it is shown that the anisotropic electron mass in the L-valley leads to two distinct terahertz absorption resonances separated by 0.8 meV.