Quantized coexisting electrons and holes in graphene measured using temperature dependent magneto-transport

TL;DR

This study investigates temperature-dependent magneto-transport in graphene near charge neutrality, revealing large potential fluctuations, strong localization effects, and unusual Hall resistivity behavior due to coexisting electrons and holes in a quantized spectrum.

Contribution

It provides the first detailed measurement of potential fluctuations in graphene and models the peculiar Hall resistivity overshoot in the presence of coexisting charge carriers.

Findings

Potential fluctuations are about 20 meV, larger than in conventional semiconductors.

Charge carriers exhibit strong localization up to room temperature.

Hall resistivity overshoots plateau values in the quantized regime.

Abstract

We present temperature-dependent magneto-transport experiments around the charge neutrality point in graphene and determine the amplitude of potential fluctuations $s$ responsible for the formation of electron-hole puddles. The experimental value $s \approx 20$ meV is considerably larger than in conventional semiconductors which implies a strong localization of charge carriers observable up to room temperature. Surprisingly, in the quantized regime, the Hall resistivity overshoots the highest plateau values at high temperatures. We demonstrate by model calculations that such a peculiar behavior is expected in any system with coexisting electrons and holes when the energy spectrum is quantized and the carriers are partially localized.