Dynamic Nuclear Polarization in the Fractional Quantum Hall Regime

TL;DR

This paper explores how dynamic nuclear polarization affects quantum point contacts in the fractional quantum Hall regime, revealing shifts in fractional plateaus and extending the composite fermion model to include hyperfine interactions.

Contribution

It demonstrates the extension of the composite fermion framework to hyperfine coupling effects in fractional quantum Hall systems.

Findings

Fractional quantum Hall plateaus shift symmetrically around =1/2

Nuclear polarization reduces Zeeman energy

Hyperfine interactions extend composite fermion theory

Abstract

We investigate dynamic nuclear polarization in quantum point contacts (QPCs) in the integer and fractional quantum Hall regimes. Following the application of a dc bias, fractional plateaus in the QPC shift symmetrically about half filling of the lowest Landau level, \nu=1/2, suggesting an interpretation in terms of composite fermions. Polarizing and detecting at different filling factors indicates that Zeeman energy is reduced by the induced nuclear polarization. Mapping effects from integer to fractional regimes extends the composite fermion picture to include hyperfine coupling.