Ballistic transmission through a graphene bilayer

TL;DR

This paper investigates how ballistic electrons transmit through a graphene bilayer, revealing that at the Dirac point, it behaves similarly to a monolayer with pseudo-diffusive transport properties, but with a narrower energy range for this behavior.

Contribution

It provides a detailed analysis of the Fermi energy dependence of current and shot noise in a graphene bilayer, highlighting differences from monolayer behavior at the Dirac point.

Findings

At the Dirac point, bilayer transmits as two monolayers in parallel.

The Fano factor at the Dirac point is 1/3, same as in monolayers and diffusive metals.

The pseudo-diffusive regime is narrower in bilayers by a factor of interlayer coupling length over sample length.

Abstract

We calculate the Fermi energy dependence of the (time-averaged) current and shot noise in an impurity-free carbon bilayer (length $L\ll$ width $W$), and compare with known results for a monolayer. At the Dirac point of charge neutrality, the bilayer transmits as two independent monolayers in parallel: Both current and noise are resonant at twice the monolayer value, so that their ratio (the Fano factor) has the same 1/3 value as in a monolayer -- and the same value as in a diffusive metal. The range of Fermi energies around the Dirac point within which this pseudo-diffusive result holds is smaller, however, in a bilayer than in a monolayer (by a factor $l_{\perp}/L$, with $l_{\perp}$ the interlayer coupling length).