Unusual charge density wave introduced by Janus structure in monolayer vanadium dichalcogenides

TL;DR

This study reports the discovery of an unusual charge density wave state in Janus monolayer VTeSe, created via surface selenization, revealing new electronic properties and symmetry-breaking phenomena in 2D transition metal dichalcogenides.

Contribution

The paper demonstrates the fabrication and experimental visualization of a novel root13-root13 CDW state in Janus VTeSe, supported by theoretical analysis beyond conventional electron-phonon interactions.

Findings

Observation of a root13-root13 CDW with threefold symmetry breaking

Experimental visualization using scanning tunneling microscopy

Theoretical explanation involving charge modulation beyond electron-phonon coupling

Abstract

As a fundamental structural feature, the symmetry of materials determines the exotic quantum properties in transition metal dichalcogenides (TMDs) with charge density wave (CDW). Breaking the inversion symmetry, the Janus structure, an artificially constructed lattice, provides an opportunity to tune the CDW states and the related properties. However, limited by the difficulties in atomic-level fabrication and material stability, the experimental visualization of the CDW states in 2D TMDs with Janus structure is still rare. Here, using surface selenization of VTe2, we fabricated monolayer Janus VTeSe. With scanning tunneling microscopy, an unusual root13-root13 CDW state with threefold rotational symmetry breaking was observed and characterized. Combined with theoretical calculations, we find this CDW state can be attributed to the charge modulation in the Janus VTeSe, beyond the conventional electron-phonon coupling. Our findings provide a promising platform for studying the CDW states and artificially tuning the electronic properties toward the applications.