Science 361, 570–574 (2018)

Theoretical descriptions of interacting particles can become very difficult when perturbation theory does not apply. This is the case for the Coulomb interactions between electrons in graphene and so most previous work has focused on either the short- or long-range limit. This isn’t ideal because a realistic situation will combine elements of both. Ho-Kin Tang and co-workers have performed detailed, non-perturbative numerical simulations to include both effects, allowing much more accurate predictions for the properties of graphene and other Dirac materials.

Their results show that both a semimetallic phase and an insulating phase are accessible by varying parameters such as the dielectric environment, the strain in the lattice or the density of electrons. They also explain why the Fermi velocity measured in experiments is often higher than that predicted by ab initio calculations. Various Dirac materials fall in different parts of this parameter space, accounting for the range of behaviour observed in experiments.