Insensitivity of spin dynamics to the orbital angular momentum transferred from twisted light to extended semiconductors

TL;DR

This study shows that the spin dynamics in semiconductors excited by twisted light are unaffected by the orbital angular momentum of the light, with differences arising only from energy variations in finite samples.

Contribution

It demonstrates that the orbital angular momentum of twisted light does not influence spin dynamics in extended semiconductors, highlighting the robustness of spin behavior against such angular momentum transfer.

Findings

Spin dynamics are identical for light with +|l| and -|l| angular momentum.

Differences are due to energy variations, not angular momentum.

Results apply broadly to Rashba and Dresselhaus spin-orbit interactions.

Abstract

We study the spin dynamics of carriers due to the Rashba interaction in semiconductor quantum disks and wells after excitation with light with orbital angular momentum. We find that although twisted light transfers orbital angular momentum to the excited carriers and the Rashba interaction conserves their total angular momentum, the resulting electronic spin dynamics is essentially the same for excitation with light with orbital angular momentum $l=+|l|$ and $l=-|l|$. The differences between cases with different values of $|l|$ are due to the excitation of states with slightly different energies and not to the different angular momenta per se, and vanish for samples with large radii where a $k$-space quasi-continuum limit can be established. These findings apply not only to the Rashba interaction but also to all other envelope-function approximation spin-orbit Hamiltonians like the Dresselhaus coupling.