New Generation of Massless Dirac Fermions in Graphene under External Periodic Potentials

TL;DR

Applying a periodic potential to graphene can generate new massless Dirac fermions with unique properties, offering a platform for experimental exploration of these quasiparticles.

Contribution

This work demonstrates the creation of novel massless Dirac fermions in graphene through external periodic potentials, highlighting their distinct characteristics and experimental feasibility.

Findings

New massless Dirac fermions are generated near supercell Brillouin zone boundaries.

These quasiparticles exhibit anisotropic group velocity and non-collinear wavevector and pseudospin.

An energy window exists where only these quasiparticles are present, enabling experimental studies.

Abstract

We show that new massless Dirac fermions are generated when a slowly varying periodic potential is applied to graphene. These quasiparticles, generated near the supercell Brillouin zone boundaries with anisotropic group velocity, are different from the original massless Dirac fermions. The quasiparticle wavevector (measured from the new Dirac point), the generalized pseudospin vector, and the group velocity are not collinear. We further show that with an appropriate periodic potential of triangular symmetry, there exists an energy window over which the only available states are these quasiparticles, thus, providing a good system to probe experimentally the new massless Dirac fermions. The required parameters of external potentials are within the realm of laboratory conditions.