Electronic structure of a graphene superlattice with a modulated Fermi velocity

TL;DR

This paper investigates how modulating the Fermi velocity in a graphene superlattice affects its electronic structure, revealing the creation of extra Dirac points and breaking electron-hole symmetry, with implications for device fabrication.

Contribution

It demonstrates that Fermi velocity modulation in a graphene superlattice induces extra Dirac points and breaks symmetry, providing new control mechanisms for electronic properties.

Findings

Extra Dirac points are induced by periodic potential.

Fermi velocity modulation breaks electron-hole symmetry.

Control over Dirac point behavior is achievable.

Abstract

The electronic structure of a graphene superlattice composed by two periodic regions with different Fermi velocity, energy gap and electrostatic potential is investigated by using an effective Dirac-like Hamiltonian. It must be expected that the change of the Fermi velocity in one region of the graphene superlattice is equivalent to changing the width of this region keeping the Fermi velocity unchanged, provided that the time taken to charge carriers cross the region is the same. However, it is shown here that these two systems are not equivalent. We found extra Dirac points induced by the periodic potential and their location in the \textbf{k} space. It is shown that the Fermi velocity modulation breaks the symmetry between the electron and hole minibands and that it is possible to control the behavior of the extra Dirac points. The results obtained here can be used in the fabrication of graphene-based electronic devices.