Unraveling the spin polarization of the v = 5/2 fractional quantum Hall state

TL;DR

This study uses resistively detected NMR to show that the v=5/2 fractional quantum Hall state is fully spin-polarized, supporting its nonabelian nature and providing insights into its unique interaction physics.

Contribution

It provides the first direct measurement of spin polarization at v=5/2, ruling out abelian models and supporting nonabelian quantum Hall states.

Findings

v=5/2 state is fully spin-polarized

Ruling out abelian candidate models

Distinct interaction physics in the first-excited Landau level

Abstract

The fractional quantum Hall (FQH) effect at filling factor v = 5/2 has recently come under close scrutiny, as it may possess quasi-particle excitations obeying nonabelian statistics, a property sought for topologically protected quantum operations. Yet, its microscopic origin remains unidentified, and candidate model wave functions include those with undesirable abelian statistics. Here we report direct measurements of the electron spin polarization of the v = 5/2 FQH state using resistively detected nuclear magnetic resonance (NMR). We find the system to be fully polarized, which unambiguously rules out the most-likely abelian contender and thus lends strong support for the v = 5/2 state being nonabelian. Our measurements reveal an intrinsically different nature of interaction in the first-excited Landau level underlying the physics at v = 5/2.