Electronic structure and charge-density wave transition in monolayer VS_{2}

TL;DR

This study synthesizes monolayer VS_{2} and uses ARPES to reveal a charge-density wave transition occurring above room temperature, advancing understanding of its electronic properties and potential catalytic applications.

Contribution

First synthesis of epitaxial monolayer VS_{2} on bilayer graphene and direct ARPES observation of a high-temperature CDW transition.

Findings

Fermi surface with six elliptical pockets at M points

Gap opening at low temperature indicating CDW transition

CDW phase transition occurs above room temperature

Abstract

Vanadium disulfide (VS_{2}) attracts elevated interests for its charge-density wave (CDW) phase transition, ferromagnetism, and catalytic reactivity, but the electronic structure of monolayer has not been well understood yet. Here we report synthesis of epitaxial 1T VS_{2} monolayer on bilayer graphene grown by molecular-beam epitaxy (MBE). Angle-resolved photoemission spectroscopy (ARPES) measurements reveal that Fermi surface with six elliptical pockets centered at the M points shows gap opening at low temperature. Temperature-dependence of the gap size suggests existence of CDW phase transition above room temperature. Our observations provide important evidence to understand the strongly correlated electron physics and the related surface catalytic properties in two-dimensional transition-metal dichalcogenides (TMDCs).