Coherence Revivals of a Spinor Polariton Condensate from Self-induced Larmor Precession

TL;DR

This paper demonstrates persistent, stable spin precession in a polariton condensate driven by self-induced magnetic fields, enabling potential applications in optical magnetometry and spin control.

Contribution

It reveals a novel regime of long-lasting, stable spin coherence in polariton condensates caused by self-induced Larmor precession, with tunable frequency based on density.

Findings

Condensate pseudo-spin precesses over 10^5 times within 20 μs pulse.

Spin coherence persists after full precession, indicating a spin coherent state.

Larmor frequency scales with condensate density, allowing optical tuning.

Abstract

First order coherence measurements of a polariton condensate, reveal a regime where the condensate pseudo-spin precesses persistently within the driving optical pulse. Within a single 20 $\mu$s optical pulse the condensate pseudo-spin performs over $10^5$ precessions with striking frequency stability. The condensate maintains its phase coherence even after a complete precession of the spin vector, making the observed state by a definition a spin coherent state. The emergence of the precession is traced to the polariton interactions that give rise to a self-induced out-of-plane magnetic field that in turn drives the spin dynamics. We find that the Larmor oscillation frequency scales with the condensate density, enabling external tuning of this effect by optical means. The stability of the system allows for the realization of integrated optical magnetometry devices with the use of materials with enhanced exciton $g$-factor and can facilitate spin squeezing effects and active coherent control on the Bloch sphere in polariton condensates.