Pseudogap, Fermi arc, and Peierls-insulating phase induced by 3D-2D crossover in monolayer VSe2

TL;DR

This study reveals a transition from metallic to insulating states in monolayer VSe2 due to 3D-2D crossover, exhibiting pseudogap and Fermi arc phenomena similar to high-temperature cuprates, driven by charge/spin fluctuations.

Contribution

It demonstrates a novel 3D-2D crossover induced phase transition in monolayer VSe2, linking quantum confinement to emergent electronic states like pseudogap and Fermi arc.

Findings

Complete insulating state with energy gap in monolayer VSe2

Presence of pseudogap and Fermi arc above CDW temperature

Similarity to high-temperature cuprate phenomena

Abstract

One of important challenges in condensed-matter physics is to realize new quantum states of matter by manipulating the dimensionality of materials, as represented by the discovery of high-temperature superconductivity in atomic-layer pnictides and room-temperature quantum Hall effect in graphene. Transition-metal dichalcogenides (TMDs) provide a fertile platform for exploring novel quantum phenomena accompanied by the dimensionality change, since they exhibit a variety of electronic/magnetic states owing to quantum confinement. Here we report an anomalous metal-insulator transition induced by 3D-2D crossover in monolayer 1T-VSe2 grown on bilayer graphene. We observed a complete insulating state with a finite energy gap on the entire Fermi surface in monolayer 1T-VSe2 at low temperatures, in sharp contrast to metallic nature of bulk. More surprisingly, monolayer 1T-VSe2 exhibits a pseudogap with Fermi arc at temperatures above the charge-density-wave temperature, showing a close resemblance to high-temperature cuprates. This similarity suggests a common underlying physics between two apparently different systems, pointing to the importance of charge/spin fluctuations to create the novel electronic states, such as pseudogap and Fermi arc, in these materials.