Spin Polarization of the 12/5 Fractional Quantum Hall Effect

TL;DR

This study investigates the tilt magnetic field effects on the fractional quantum Hall state at filling factor 12/5, revealing non-monotonic behavior in resistance and activation energy, indicating complex ground state dynamics.

Contribution

It provides the first detailed tilt magnetic field analysis of the 12/5 fractional quantum Hall state, highlighting unique non-monotonic responses unlike the 5/2 state.

Findings

Rxx shows a non-monotonic dependence on tilt angle

Activation energy _{12/5} first decreases then reemerges with tilt

Distinct tilt response compared to the 5/2 state

Abstract

We have carried out tilt magnetic field (B) studies of the \nu=12/5 fractional quantum Hall state in an ultra-high quality GaAs quantum well specimen. Its diagonal magneto-resistance Rxx shows a non-monotonic dependence on tilt angle (\theta). It first increases sharply with increasing \theta, reaches a maximal value of ~ 70 ohms at \theta ~ 14^o, and then decreases at higher tilt angles. Correlated with this dependence of Rxx on \theta, the 12/5 activation energy (\Delta_{12/5}) also shows a non-monotonic tilt dependence. \Delta_{12/5} first decreases with increasing \theta. Around \theta = 14^{o}, \Delta_{12/5} disappears as Rxx becomes non-activated. With further increasing tilt angles, \Delta_{12/5} reemerges and increases with \theta. This tilt B dependence at \nu=12/5 is strikingly different from that of the well-documented 5/2 state and calls for more investigations on the nature of its ground state.