Artificial graphenes: Dirac matter beyond condensed matter

TL;DR

This paper reviews the development of artificial graphenes, which are engineered systems mimicking graphene's Dirac cones, allowing for novel experiments and control over topological properties beyond traditional condensed matter systems.

Contribution

It provides a comprehensive overview of various artificial graphene systems and discusses how they enable new physical phenomena and control over Dirac points not possible in natural graphene.

Findings

Artificial systems can control Dirac point existence and position.

Experimental investigations reveal scenarios of Dirac point merging and emergence.

Topological charge conservation governs Dirac cone manipulation.

Abstract

After the discovery of graphene and its many fascinating properties, there has been a growing interest for the study of "artificial graphenes". These are totally different and novel systems which bear exciting similarities with graphene. Among them are lattices of ultracold atoms, microwave or photonic lattices, "molecular graphene" or new compounds like phosphorene. The advantage of these structures is that they serve as new playgrounds for measuring and testing physical phenomena which may not be reachable in graphene, in particular: the possibility of controlling the existence of Dirac points (or Dirac cones) existing in the electronic spectrum of graphene, of performing interference experiments in reciprocal space, of probing geometrical properties of the wave functions, of manipulating edge states, etc. These cones, which describe the band structure in the vicinity of the two connected energy bands, are characterized by a topological "charge". They can be moved in reciprocal space by appropriate modification of external parameters (pressure, twist, sliding, stress, etc.). They can be manipulated, created or suppressed under the condition that the total topological charge be conserved. In this short review, I discuss several aspects of the scenarios of merging or emergence of Dirac points as well as the experimental investigations of these scenarios in condensed matter and beyond.