Shot Noise in Ballistic Graphene

TL;DR

This study measures shot noise in graphene devices at low temperatures, revealing a maximum Fano factor of about 1/3 at the Dirac point, consistent with evanescent state transport theory.

Contribution

It provides experimental evidence of shot noise behavior in graphene, confirming theoretical predictions about evanescent mode transport at the Dirac point.

Findings

Fano factor peaks at ~1/3 at Dirac point

Fano factor decreases with increasing charge density

Results agree with evanescent state transport theory

Abstract

We have investigated shot noise in graphene field effect devices in the temperature range of 4.2--30 K at low frequency ($f$ = 600--850 MHz). We find that for our graphene samples with large width over length ratio $W/L$, the Fano factor $\mathfrak{F}$ reaches a maximum $\mathfrak{F} \sim$ 1/3 at the Dirac point and that it decreases strongly with increasing charge density. For smaller $W/L$, the Fano factor at Dirac point is significantly lower. Our results are in good agreement with the theory describing that transport at the Dirac point in clean graphene arises from evanescent electronic states.