Optical absorption to probe the quantum Hall ferromagnet at filling factor $\nu=1$

TL;DR

This study uses optical absorption to investigate spin polarization in quantum Hall systems, revealing that the ferromagnetic state at filling factor ν=1 is highly sensitive to temperature and filling factor variations.

Contribution

It demonstrates the fragility of the quantum Hall ferromagnet at ν=1 through optical absorption measurements, highlighting its sensitivity to temperature and filling factor changes.

Findings

Full spin polarization only at ν=1 and very low temperatures

Small changes in filling factor cause significant depolarization

The ferromagnetic state is fragile against temperature and filling factor variations

Abstract

Optical absorption measurements are used to probe the spin polarization in the integer and fractional quantum Hall effect regimes. The system is fully spin polarized only at filling factor $\nu=1$ and at very low temperatures($\sim40$ mK). A small change in filling factor ($\delta\nu\approx\pm0.01$) leads to a significant depolarization. This suggests that the itinerant quantum Hall ferromagnet at $\nu=1$ is surprisingly fragile against increasing temperature, or against small changes in filling factor.