Emergence of Superlattice Dirac Points in Graphene on Hexagonal Boron Nitride

TL;DR

This paper demonstrates that a Moiré pattern in graphene on hexagonal boron nitride creates superlattice Dirac points, leading to new massless Dirac fermions with reduced Fermi velocity and anisotropic electronic properties.

Contribution

It provides experimental and theoretical evidence that Moiré patterns induce superlattice Dirac points in graphene on hBN, revealing new electronic phenomena.

Findings

Emergence of superlattice Dirac points due to Moiré pattern

Reduced Fermi velocity at new Dirac points

Hexagonal modulation of local density of states

Abstract

The Schr\"odinger equation dictates that the propagation of nearly free electrons through a weak periodic potential results in the opening of band gaps near points of the reciprocal lattice known as Brillouin zone boundaries. However, in the case of massless Dirac fermions, it has been predicted that the chirality of the charge carriers prevents the opening of a band gap and instead new Dirac points appear in the electronic structure of the material. Graphene on hexagonal boron nitride (hBN) exhibits a rotation dependent Moir\'e pattern. In this letter, we show experimentally and theoretically that this Moir\'e pattern acts as a weak periodic potential and thereby leads to the emergence of a new set of Dirac points at an energy determined by its wavelength. The new massless Dirac fermions generated at these superlattice Dirac points are characterized by a significantly reduced Fermi velocity. The local density of states near these Dirac cones exhibits hexagonal modulations indicating an anisotropic Fermi velocity.