NMR probing of the spin polarization of the nu=5/2 quantum Hall state

TL;DR

This study uses resistively detected NMR to measure the electron spin polarization of the fractional quantum Hall state at filling factor 5/2, confirming it is fully polarized as predicted by Moore-Read theory.

Contribution

It provides the first direct NMR measurement of the spin polarization of the 5/2 quantum Hall state, validating a key theoretical assumption.

Findings

The 5/2 state is fully spin polarized within experimental error.

NMR detection is possible at electron temperatures as low as 30 mK.

Electron heating effects under RF excitation are characterized.

Abstract

Resistively detected nuclear magnetic resonance is used to measure the Knight shift of the As nuclei and determine the electron spin polarization of the fractional quantum Hall states of the second Landau level. We show that the 5/2 state is fully polarized within experimental error, thus confirming a fundamental assumption of the Moore-Read theory. We measure the electron heating under radio frequency excitation, and show that we are able to detect NMR at electron temperatures down to 30 mK.