Quantum Hall effect near the charge neutrality point in two-dimensional electron-hole system

TL;DR

This study investigates the quantum Hall effect near the charge neutrality point in HgTe quantum wells with electrons and holes, revealing unique transport behaviors linked to electron-hole interactions and snake states.

Contribution

It provides new insights into the quantum Hall effect at charge neutrality in electron-hole systems, highlighting the role of snake states and drawing parallels with graphene.

Findings

Resistance increases strongly with magnetic field at CNP

Hall resistivity approaches zero at CNP

Presence of a wide Hall conductivity plateau near zero

Abstract

We study the transport properties of $HgTe$-based quantum wells containing simultaneously electrons and holes in magnetic field B. At the charge neutrality point (CNP) with nearly equal electron and hole densities, the resistance is found to increase very strongly with B while the Hall resistivity turns to zero. This behavior results in a wide plateau in the Hall conductivity $\sigma_{xy}\approx 0$ and in a minimum of diagonal conductivity $\sigma_{xx}$ at $\nu=\nu_p-\nu_n=0$, where $\nu_n$ and $\nu_p$ are the electron and hole Landau filling factors. We suggest that the transport at the CNP point is determined by electron-hole "snake states" propagating along the $\nu=0$ lines. Our observations are qualitatively similar to the quantum Hall effect in graphene as well as to the transport in random magnetic field with zero mean value.