Absence of Floating Delocalized States in a Two-Dimensional Hole Gas

TL;DR

This study investigates the behavior of delocalized states in a two-dimensional hole gas within a GaAs/AlGaAs heterostructure, revealing their absence at zero magnetic field, which contrasts with electron systems and may relate to the metal-insulator transition.

Contribution

It provides the first detailed phase diagram of delocalized states in a 2D hole gas and shows their energy flattening at zero magnetic field, differing from electron systems.

Findings

Delocalized state energy flattens as magnetic field approaches zero.

No divergence of delocalized states at zero magnetic field in hole systems.

Potential link to the metal-insulator transition at B=0.

Abstract

By tracking the delocalized states of the two-dimensional hole gas in a p-type GaAs/AlGaAs heterostructure as a function of magnetic field, we mapped out a phase diagram in the density-magnetic-field plane. We found that the energy of the delocalized state from the lowest Landau level flattens out as the magnetic field tends toward zero. This finding is different from that for the two-dimensional electron system in an n-type GaAs/AlGaAs heterostructure where delocalized states diverge in energy as B goes to zero indicating the presence of only localized states below the Fermi energy. The possible connection of this finding to the recently observed metal-insulator transition at B = 0 in the two-dimensional hole gas systems is discussed.