Charge transport in ballistic multiprobe graphene structures

TL;DR

This paper investigates the transport properties of multiterminal ballistic graphene, highlighting the transition from propagating to evanescent modes near the Dirac point and their effects on conductance and correlations.

Contribution

It provides new insights into how evanescent modes near the Dirac point influence conductance matrices and cross-correlations in graphene devices.

Findings

Propagating modes dominate far from Dirac point.

Evanescent modes affect conductance near Dirac point.

Cross correlations reveal evanescent mode effects.

Abstract

We study the the transport properties of multiterminal ballistic graphene samples, concentrating on the conductance matrix, fluctuations and cross-correlations. Far away from Dirac point, the current is carried mostly by propagating modes and the results can be explained with the conventional semiclassical picture familiar from ray optics, where electrons propagate along a single direction before scattering or reaching the terminals. However, close to the Dirac point the transport is due to evanescent modes which do not have to follow a rectilinear path. As we show in this Letter, this property of the evanescent modes influences the conductance matrix. However, at best it can be observed by measuring the cross correlations in an exchange Hanbury Brown-Twiss experiment.