Monopolar Optical Orientation of Electronic Spins in Semiconductors

TL;DR

This paper demonstrates that circularly polarized infrared radiation can induce monopolar spin orientation of free electrons in semiconductors and quantum wells, with experimental evidence from spin-galvanic and circular photogalvanic effects.

Contribution

It reveals a new mechanism for spin orientation via intraband and intra-subband transitions in n-type semiconductors and quantum wells, including the role of valence band admixture and spin-orbit splitting.

Findings

Spin polarization observed in quantum wells.

Monopolar spin orientation achievable in n-type materials.

Experimental evidence from spin-galvanic and photogalvanic effects.

Abstract

It is shown that absorption of circularly polarized infrared radiation due to intraband (Drude-like) transitions in n-type bulk semiconductors and due to intra-subband or inter-subband transitions in quantum well (QW) structures results in a monopolar spin orientation of free electrons. Spin polarization in zinc-blende-structure based QWs is demonstrated by the observation of the spin-galvanic and the circular photogalvanic effects. The monopolar spin orientation in n-type materials is shown to be 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.