Magnetic field induced nutation of the exciton-polariton polarization in (Cd,Zn)Te crystals

TL;DR

This study investigates how magnetic fields induce polarization nutation in exciton-polaritons within (Cd,Zn)Te crystals, revealing complex spectral and magnetic field dependencies of magneto-optical effects and polarization dynamics.

Contribution

It provides the first detailed analysis of magnetic field-induced polarization nutation of exciton-polaritons in (Cd,Zn)Te crystals, including a comprehensive model explaining the observed effects.

Findings

Polarization oscillations reach 10 GHz at 5 T.

Strong dispersion causes pulse stretching to 200-300 ps.

Spectral dependence of Faraday rotation affects polarization behavior.

Abstract

We study the polarization dynamics of exciton-polaritons propagating in sub-mm thick (Cd,Zn)Te bulk crystals using polarimetric time-of-flight techniques. The application of a magnetic field in Faraday geometry leads to synchronous temporal oscillations of all Stokes parameters of an initially linearly or circularly polarized, spectrally broad optical pulse of 150 fs duration propagating through the crystal. Strong dispersion for photon energies close to the exciton resonance leads to stretching of the optical pulse to a duration of 200$-$300 ps and enhancement of magneto-optical effects such as the Faraday rotation and the non-reciprocal birefringence. The oscillation frequency of the exciton-polariton polarization increases with magnetic field $B$, reaching 10 GHz at $B\sim 5$T. Surprisingly, the relative contributions of Faraday rotation and non-reciprocal birefringence undergo strong changes with photon energy, which is attributed to a non-trivial spectral dependence of Faraday rotation in the vicinity of the exciton resonance. This leads to polarization nutation of the transmitted optical pulse in the time domain. The results are well explained by a model that accounts for Faraday rotation and magneto-spatial dispersion in zinc-blende crystals. We evaluate the exciton $g$-factor $|g_{\rm exc}|=0.2$ and the magneto-spatial constant $V= 5 \times 10^{-12}$ eVcm$\textup{T}^{-1}$.