Experimental Observation of Quantum Hall Effect and Berry's Phase in Graphene

TL;DR

This paper reports the experimental observation of the quantum Hall effect and Berry's phase in graphene, revealing relativistic Dirac fermion behavior and topological properties of its band structure.

Contribution

It provides the first experimental evidence of half-integer quantum Hall effect and Berry's phase in graphene, highlighting its unique relativistic electronic properties.

Findings

Observation of half-integer quantum Hall effect in graphene

Detection of vanishing effective mass at the Dirac point

Confirmation of Berry's phase through magneto-oscillation phase shift

Abstract

When electrons are confined in two-dimensional (2D) materials, quantum mechanically enhanced transport phenomena, as exemplified by the quantum Hall effects (QHE), can be observed. Graphene, an isolated single atomic layer of graphite, is an ideal realization of such a 2D system. Here, we report an experimental investigation of magneto transport in a high mobility single layer of graphene. Adjusting the chemical potential using the electric field effect, we observe an unusual half integer QHE for both electron and hole carriers in graphene. Vanishing effective carrier masses is observed at Dirac point in the temperature dependent Shubnikov de Haas oscillations, which probe the 'relativistic' Dirac particle-like dispersion. The relevance of Berry's phase to these experiments is confirmed by the phase shift of magneto-oscillations, related to the exceptional topology of the graphene band structure.