A Quantized $\nu =5/2$ State in a Two-Subband Quantum Hall System

TL;DR

This study investigates the fractional quantum Hall state at filling 5/2 in wide quantum wells, revealing its persistence or disappearance depending on well width and subband occupancy, highlighting the role of intersubband interactions.

Contribution

It demonstrates how well width and subband occupancy influence the stability of the 5/2 fractional quantum Hall state in two-subband systems, providing new insights into subband effects.

Findings

The 5/2 state persists in 80 and 60 nm wells with two subbands occupied.

The 5/2 state vanishes in 50 nm wells when the second subband is populated.

The behavior is linked to capacitive energy and subband wavefunction overlap.

Abstract

The evolution of the fractional quantum Hall state at filling 5/2 is studied in density tunable two-dimensional electron systems formed in wide wells in which it is possible to induce a transition from single to two subband occupancy. In 80 and 60 nm wells, the quantum Hall state at 5/2 filling of the lowest subband is observed even when the second subband is occupied. In a 50 nm well the 5/2 state vanishes upon second subband population. We attribute this distinct behavior to the width dependence of the capacitive energy for intersubband charge transfer and of the overlap of the subband probability densities.