Tuning the Fano factor of graphene via Fermi velocity modulation

TL;DR

This paper explores how modulating the Fermi velocity in graphene superlattices can control the Fano factor, revealing new ways to identify the Dirac point and tune electronic properties.

Contribution

It introduces a method to tune the Fano factor peak and Dirac point in graphene via Fermi velocity modulation, especially in the presence of an energy gap.

Findings

Fano factor peak position can be tuned by Fermi velocity modulation.

Higher Fermi velocities can reduce the Fano factor below 1/3.

Symmetry in Fano factor peaks is broken in quasi-periodic superlattices.

Abstract

In this work we investigate the influence of a Fermi velocity modulation on the Fano factor of periodic and quasi-periodic graphene superlattices. We consider the continuum model and use the transfer matrix method to solve the Dirac-like equation for graphene where the electrostatic potential, energy gap and Fermi velocity are piecewise constant functions of the position x. We found that in the presence of an energy gap, it is possible to tune the energy of the Fano factor peak and consequently the location of the Dirac point, by a modulations in the Fermi velocity. Hence, the peak of the Fano factor can be used experimentally to identify the Dirac point. We show that for higher values of the Fermi velocity the Fano factor goes below 1/3 in the Dirac point. Furthermore, we show that in periodic superlattices the location of Fano factor peaks is symmetric when the Fermi velocity $v_A$ and $v_B$ is exchanged, however by introducing quasi-periodicity the symmetry is lost. The Fano factor usually holds a universal value for a specific transport regime, which reveals that the possibility of controlling it in graphene is a notable result.