Emergence of a Metal-Insulator Transition and High Temperature Charge Density Waves in VSe2 at the Monolayer Limit

TL;DR

This study reveals that monolayer VSe2 on graphene exhibits a high-temperature charge density wave transition and a metal-insulator transition driven by electronic reconstructions and lattice distortions, highlighting the influence of heterointerfaces.

Contribution

The paper demonstrates that heterointerfaces induce perfect Fermi-surface nesting and significantly elevate the charge density wave transition temperature in monolayer VSe2.

Findings

Charge density wave transition temperature increased to 350 K

Observation of a metal-insulator transition at 135 K

Perfect Fermi-surface nesting in monolayer VSe2

Abstract

Emergent phenomena driven by electronic reconstructions in oxide heterostructures have been intensively discussed. However, the role of these phenomena in shaping the electronic properties in van der Waals heterointerfaces has hitherto not been established. By reducing the material thickness and forming a heterointerface, we find two types of charge-ordering transitions in monolayer VSe2 on graphene substrates. Angle-resolved photoemission spectroscopy (ARPES) uncovers that Fermi-surface nesting becomes perfect in ML VSe2. Renormalization group analysis confirms that imperfect nesting in three dimensions universally flows into perfect nesting in two dimensions. As a result, the charge density wave transition temperature is dramatically enhanced to a value of 350 K compared to the 105 K in bulk VSe2. More interestingly, ARPES and scanning tunneling microscopy measurements confirm an unexpected metal-insulator transition at 135 K, driven by lattice distortions. The heterointerface plays an important role in driving this novel metal-insulator transition in the family of monolayered transition metal dichalcogenides.