Plasmon to exciton spin conversion in semiconductor-metal hybrid structures

TL;DR

This paper demonstrates ultrafast optical excitation of electron spins via plasmon to exciton conversion in hybrid structures, enabling controlled spin orientation in a plane using plasmonic polarization tailoring.

Contribution

It introduces a method for ultrafast spin control through plasmonic excitation, allowing arbitrary spin orientation in a 2D plane, which is a novel approach in spintronics.

Findings

Ultrafast femtosecond spin excitation via plasmon to exciton conversion.

Spin orientation is locked to surface plasmon-polariton propagation direction.

Photon spin can be used to control electron spin orientation arbitrarily.

Abstract

Optical control of electronic spins is the basis for ultrafast spintronics: circularly polarized light in combination with spin-orbit coupling of the electronic states allows for spin manipulation in condensed matter. However, the conventional approach is limited to spin orientation along one particular orientation that is dictated by the direction of photon propagation. Plasmonics opens new capabilities, allowing one to tailor the light polarization at the nanoscale. Here, we demonstrate ultrafast optical excitation of electron spin on femtosecond time scales via plasmon to exciton spin conversion. By time-resolving the THz spin dynamics in a hybrid (Cd,Mn)Te quantum well structure covered with a metallic grating, we unambiguously determine the orientation of the photoexcited electron spins which is locked to the propagation direction of surface plasmon-polaritons. Using the spin of the incident photons as additional degree of freedom, one can orient the photoexcited electron spin at will in a two-dimensional plane.