Spin Transition in the \nu=8/3 Fractional Quantum Hall Effect

TL;DR

This study investigates the spin transition in the fractional quantum Hall effect at filling factor 8/3, revealing a density-induced spin transition through activation energy gap measurements in high-quality quantum wells.

Contribution

It provides experimental evidence of a spin transition at u=8/3, a phenomenon not previously characterized in detail, using density-dependent energy gap measurements.

Findings

7/3 energy gap increases monotonically with density

8/3 energy gap shows a non-monotonic behavior indicating a spin transition

Evidence supports a density-driven spin polarization change at u=8/3

Abstract

We present here the results from a density dependent study of the activation energy gaps of the fractional quantum Hall effect states at Landau level fillings \nu=8/3 and 7/3 in a series of high quality quantum wells. In the density range from 0.5 x 10^{11} to 3 x 10^{11} cm^{-2}, the 7/3 energy gap increases monotonically with increasing density, supporting its ground state being spin polarized. For the 8/3 state, however, its energy gap first decreases with increasing density, almost vanishes at n ~ 0.8 x 10^{11} cm^{-2}, and then turns around and increases with increasing density, clearly demonstrating a spin transition.