Current Induced Nuclear Spin Depolarization at Landau Level Filling Factor nu=1/2

TL;DR

This study demonstrates that applying an electric current in a quantum Hall system at filling factor nu=1/2 can significantly depolarize nuclear spins through hyperfine interactions, revealing insights into electron-nuclear coupling and electron temperature effects.

Contribution

It introduces a method to manipulate nuclear spin polarization via current at nu=1/2 and highlights the importance of electron wavefunction thickness and heating effects in this process.

Findings

Current induces nuclear spin depolarization at nu=1/2.

Nuclear polarization follows Curie law with electron temperature.

Electron g-factor and polarization mass are evaluated.

Abstract

Hyperfine interactions between electron and nuclear spins in the quantum Hall regime provide powerful means for manipulation and detection of nuclear spins. In this work we demonstrate that significant changes in nuclear spin polarization can be created by applying an electric current in a 2-dimensional electron system at Landau level filling factor nu=1/2. Electron spin transitions at nu= 2/3 and 1/2 are utilized for the measurement of the nuclear spin polarization. Consistent results are obtained from these two different methods of nuclear magnetometry. The finite thickness of the electron wavefunction is found to be important even for a narrow quantum well. The current induced effect on nuclear spins can be attributed to electron heating and the efficient coupling between the nuclear and electron spin systems at nu=1/2. The electron temperature, elevated by the current, can be measured with a thermometer based on the measurement of the nuclear spin relaxation rate. The nuclear spin polarization follows a Curie law dependence on the electron temperature. This work also allows us to evaluate the electron g-factor in high magnetic fields as well as the polarization mass of composite fermions.