Optical Spin Orientation under Inter- and Intra-Subband Transitions in QWs

TL;DR

This paper demonstrates that circularly polarized infrared radiation can induce monopolar spin orientation in quantum wells through inter- and intra-subband transitions, confirmed by observed spin-galvanic and circular photogalvanic effects.

Contribution

It reveals a new mechanism for spin polarization in quantum wells via infrared absorption involving inter- and intra-subband transitions, considering valence band admixture and spin-orbit effects.

Findings

Monopolar spin polarization observed in quantum wells.

Spin orientation achieved through specific optical transitions.

Confirmation via spin-galvanic and circular photogalvanic effects.

Abstract

It is shown that absorption of circularly polarized infrared radiation achieved by inter-subband and intra-subband (Drude-like) transitions results in a monopolar spin orientation of free carriers. The monopolar spin polarization in zinc-blende-based quantum wells (QWs) is demonstrated by the observation of the spin-galvanic and circular photogalvanic effects. It is shown that monopolar spin orientation in n-type QWs becomes possible if an admixture of valence band states to the conduction band wave function and the spin-orbit splitting of the valence band are taken into account.