Probing charge order of monolayer NbSe$_2$ within a bulk crystal

TL;DR

This study investigates how the charge density wave (CDW) order in monolayer NbSe$_2$ is affected by dimensionality, revealing a significant enhancement of the CDW transition temperature when embedded in a bulk matrix.

Contribution

The paper demonstrates a novel experimental approach using misfit crystals to probe monolayer NbSe$_2$ within a bulk environment, revealing enhanced CDW properties.

Findings

Nearly sixfold increase in CDW transition temperature in monolayer NbSe$_2$

Effective monolayer electronic behavior observed in misfit crystal

Dimensionality significantly influences charge order in NbSe$_2"

Abstract

Atomically thin transition metal dichalcogenides can exhibit markedly different electronic properties compared to their bulk counterparts. In the case of NbSe$_2$, the question of whether its charge density wave (CDW) phase is enhanced in the monolayer limit has been the subject of intense debate, primarily due to the difficulty of decoupling this order from its environment. Here, we address this challenge by using a misfit crystal that comprises NbSe$_2$ monolayers separated by SnSe rock-salt spacers, a structure that allows us to investigate a monolayer crystal embedded in a bulk matrix. We establish an effective monolayer electronic behavior of the misfit crystal by studying its transport properties and visualizing its electronic structure by angle-resolved photoemission measurements. We then investigate the emergence of the CDW by tracking the temperature dependence of its collective modes. Our findings reveal a nearly sixfold enhancement in the CDW transition temperature, providing compelling evidence for the profound impact of dimensionality on charge order formation in NbSe$_2$.