Charge and Spin Transport at the Quantum Hall Edge of Graphene

TL;DR

This paper explores the unique charge and spin transport phenomena at the quantum Hall edge of graphene, highlighting the role of Dirac electrons, Zeeman splitting, and potential for spintronics applications.

Contribution

It introduces a microscopic framework for understanding quantum Hall edge states in graphene, emphasizing the impact of Dirac character and Zeeman effects on spin transport.

Findings

Zeeman splitting creates counter-circulating spin modes

Graphene exhibits a large Zeeman spin gap suitable for spintronics

Proposed scanning tunneling method to map edge state dispersion

Abstract

Landau level bending near the edge of graphene, described using 2d Dirac equation, provides a microscopic framework for understanding the quantum Hall Effect (QHE) in this material. We review properties of the QHE edge states in graphene, with emphasis on the novel phenomena that arise due to Dirac character of electronic states. A method of mapping out the dispersion of the edge states using scanning tunneling probes is proposed. The Zeeman splitting of Landau levels is shown to create a particularly interesting situation around the Dirac point, where it gives rise to counter-circulating modes with opposite spin. These chiral spin modes lead to a rich variety of spin transport phenomena, including spin Hall effect, spin filtering and injection, and electric detection of spin current. The estimated Zeeman spin gap, enhanced by exchange, of a few hundred Kelvin, makes graphene an attractive system for spintronics. Comparison to recent transport measurements near nu=0 is presented.