Parametric Inversion of Spin Currents in Semiconductor Microcavities

TL;DR

This paper demonstrates that exciton-polariton parametric scattering in semiconductor microcavities can reverse the sign of spin currents generated by the optical spin-Hall effect, revealing a nonlinear control mechanism.

Contribution

It introduces a method to invert spin currents in microcavities using parametric scattering, advancing control over spin dynamics in polaritonic systems.

Findings

Reversal of spin current sign via parametric scattering.

Observation of spin current inversion at high pump intensities.

Confirmation of nonlinear control over optical spin-Hall effect.

Abstract

The optical spin-Hall effect results in the formation of an antisymmetric real space polarization pattern forming spin currents. In this paper, we show that the exciton-polariton parametric scattering allows us to reverse the sign of these currents. We describe the pulsed resonant excitation of a strongly coupled microcavity with a linearly polarized pump at normal incidence. The energy of the pulse is set to be close to the inflexion point of the polariton dispersion and the focusing in real space populates the reciprocal space on a ring. For pumping powers below the parametric scattering threshold, the propagation of the injected polaritons in the effective magnetic field induced by the TE and TM splitting produce the normal optical spin-Hall effect. Keeping the same input polarization but increasing the pump intensity, the parametric scattering towards an idler and a signal state is triggered on the whole elastic circle. The injected particles are scattered toward these states while propagating radially all over the plane, gaining a cross linear polarisation with respect to the pump during the nonlinear process. Eventually, the propagation of the polaritons in the effective field results in the optical spin Hall-effect, but this time with inverted polarization domains.