Electronic structure of two-dimensional crystals from ab-initio theory

TL;DR

This paper presents ab-initio calculations of the electronic structures of recently synthesized two-dimensional materials like MoS2, NbSe2, Si, and Ge, revealing their semiconducting or metallic nature and comparing their properties to graphene.

Contribution

It provides detailed ab-initio insights into the electronic properties of 2D crystals, including MoS2, NbSe2, Si, and Ge, and compares them to graphene, highlighting differences in Dirac cone features.

Findings

MoS2 is a semiconductor with a gap close to its 3D form

NbSe2 remains metallic in 2D, similar to its 3D counterpart

Hexagonal Ge is metallic without Dirac cone features

Abstract

We report on ab-initio calculations of the two-dimensional systems MoS2 and NbSe2, which recently were synthesized. We find that two-dimensional MoS$_2$ is a semiconductor with a gap which is rather close to that of the three dimensional analogue, and that NbSe$_2$ is a metal, which is similar to the three dimensional analogue of this compound. We further computed the electronic structure of the two-dimensional hexagonal (graphene like) lattices of Si and Ge, and compare them with the electronic structure of graphene. It is found that the properties related to the Dirac cone do not appear in the case of two-dimensional hexagonal germanium, which is metallic, contrary to two-dimensional hexagonal silicon, which has an electronic structure very similar to the one of graphene, making them possibly equivalent.