Spin and orbital mechanisms of the magneto-gyrotropic photogalvanic effects in GaAs/AlGaAs quantum well structures

TL;DR

This study investigates the spin and orbital contributions to magneto-gyrotropic photogalvanic effects in GaAs/AlGaAs quantum wells, revealing spin dominance in most cases and orbital effects in structures with negligible g* factors.

Contribution

It uniquely separates spin and orbital mechanisms of MPGE in quantum wells by exploiting the dependence of the Landé factor g* on well width.

Findings

MPGE is mainly driven by spin mechanisms in most quantum wells.

Orbital mechanisms are observed in structures with near-zero g* factor.

Photocurrent correlates with the g* factor in the studied structures.

Abstract

We report on the study of the linear and circular magneto-gyrotropic photogalvanic effect (MPGE) in GaAs/AlGaAs quantum well structures. Using the fact that in such structures the Land\'e-factor g* depends on the quantum well (QW) width and has different signs for narrow and wide QWs, we succeeded to separate spin and orbital contributions to both MPGEs. Our experiments show that, for most quantum well widths, the PGEs are mainly driven by spin-related mechanisms, which results in a photocurrent proportional to the g* factor. In structures with a vanishingly small g* factor, however, linear and circular MPGE are also detected, proving the existence of orbital mechanisms.