Long-living dark coherence brought to light by magnetic-field controlled photon echo

TL;DR

This paper reveals a new photon echo regime that uncovers long-lived dark optical coherence by exploiting magnetic-field effects and differing dephasing rates, demonstrated in quantum well excitons.

Contribution

It introduces a novel non-oscillating photon echo regime that enables observation of dark coherence, advancing understanding of spin and optical coherence dynamics.

Findings

Observation of a non-oscillating photon echo regime.

Demonstration of long-living dark optical coherence.

Application to excitons in quantum wells.

Abstract

Larmor precession of the quasiparticle spin about a transverse magnetic field leads to the oscillations in the spontaneous photon echo signal due to the shuffling of the optical coherence between optically accessible (bright) and inaccessible (dark) states. Here we report on a new non-oscillating photon echo regime observed in the presence of non-equal dephasing rates of bright and dark states. This regime enables the observation of the long-living dark optical coherence. As a simple mechanical analogy, we suggest a charged particle moving in the magnetic field through the medium with anisotropic viscous friction. We demonstrate the dark coherence retrieval in the spontaneous photon echo from excitons in the InGaAs/GaAs quantum well.