Twisted-light-induced optical transitions in semiconductors: Free-carrier quantum kinetics

TL;DR

This paper develops a theoretical framework extending Semiconductor Bloch Equations to analyze how twisted light induces interband transitions and affects electron dynamics in semiconductors, revealing angular momentum transfer and current densities.

Contribution

It introduces a cylindrical coordinate-based extension of semiconductor Bloch Equations to describe twisted light interactions with semiconductors, providing analytical solutions in the low excitation regime.

Findings

Derived analytical expressions for electron coherences and populations.

Quantified orbital angular momentum transfer from light to electrons.

Calculated electric current densities induced by twisted light.

Abstract

We theoretically investigate the interband transitions and quantum kinetics induced by light carrying orbital angular momentum, or twisted light, in bulk semiconductors. We pose the problem in terms of the Heisenberg equations of motion of the electron populations, and inter- and intra-band coherences. Our theory extends the free-carrier Semiconductor Bloch Equations to the case of photo-excitation by twisted light. The theory is formulated using cylindrical coordinates, which are better suited to describe the interaction with twisted light than the usual cartesian coordinates used to study regular optical excitation. We solve the equations of motion in the low excitation regime, and obtain analytical expressions for the coherences and populations; with these, we calculate the orbital angular momentum transferred from the light to the electrons and the paramagnetic and diamagnetic electric current densities.