Optically Induced Nuclear Spin Polarization in the Quantum Hall Regime: The Effect of Electron Spin Polarization through Exciton and Trion Excitations

TL;DR

This study investigates how optically pumped electron spins in the quantum Hall regime influence nuclear spin polarization, revealing a complex dependence on filling factor mediated by excitons and trions.

Contribution

It introduces a novel estimation method for electron spin polarization and demonstrates its role in nuclear spin polarization via excitonic complexes.

Findings

Nuclear magnetic field $B_N$ shows a non-monotonous dependence on filling factor.

Excitons and trions participate in nuclear spin polarization.

Electron spin polarization effects are elucidated through circularly polarized photoluminescence.

Abstract

We study nuclear spin polarization in the quantum Hall regime through the optically pumped electron spin polarization in the lowest Landau level. The nuclear spin polarization is measured as a nuclear magnetic field $B_N$ by means of the sensitive resistive detection. We find the dependence of $B_N$ on filling factor unmonotonous. The comprehensive measurements of $B_N$ with the help of the circularly polarized photoluminescence measurements indicate the participation of the photo-excited complexes i.e., the exciton and trion (charged exciton), in nuclear spin polarization. On the basis of a novel estimation method of the equilibrium electron spin polarization, we analyze the experimental data and conclude that the filling factor dependence of $B_N$ is understood by the effect of electron spin polarization through excitons and trions.