Absorption in the fractional quantum Hall regime: trion dichroism and spin polarization

TL;DR

This study uses optical absorption measurements to probe spin polarization in the fractional quantum Hall regime, revealing full polarization at nu=1/3 and gradual depolarization near nu=2/3, indicating complex spin states.

Contribution

It demonstrates that circular dichroism of singlet trion absorption can serve as an effective probe of spin polarization in fractional quantum Hall systems.

Findings

Full spin polarization at nu=1/3

Depolarization near nu=2/3

Partial polarization persists over a broad magnetic field range

Abstract

We present measurements of optical interband absorption in the fractional quantum Hall regime in a GaAs quantum well in the range 0 < nu < 1. We investigate the mechanism of singlet trion absorption, and show that its circular dichroism can be used as a probe of the spin polarization of the ground state of the two-dimensional electron system (2DES). We find that at nu = 1/3 the 2DES is fully spin-polarized. Increasing the filling factor results in a gradual depolarization, with a sharp minimum in the dichroism near nu = 2/3. We find that in the range 0.5 < nu < 0.85 the 2DES remains partially polarized for the broad range of magnetic fields from 2.75 to 11 Tesla. This is consistent with the presence of a mixture of polarized and depolarized regions.