2D transition metal dichalcogenides: Elucidating the interplay between fermiology and exotic quantum phases


Insights from the unique correlated metallic state in monolayer NbTe2

Dr. Sugawara, the corresponding author of this research paper

The ability to manipulate exotic quantum phases—such as the Mott-insulating phase and the charge density wave (CDW) metallic states—in two-dimensional (2D) transition metal dichalcogenides (TMDs) promises novel electronic and quantum device applications.

However, realizing this vision requires a deeper understanding of the fundamental mechanisms behind the CDW-Mott phase in TMDs.

In a 2023 article, Sugawara and coworkers from AIMR addressed this gap by demonstrating that the monolayer 1T-NbTe2 is a new class of 2D TMD exhibiting a metallic ground state characterized by a sparsely occupied star-of-David lattice1.

“Other TMDs, such as 1T-NbSe2, were known to exhibit a Mott-insulating ground state coexisting with CDW order,” says Sugawara. “In this study, we wanted to investigate the ground state properties of the isostructural monolayer 1T-NbTe2, which was unknown at the time.”

Using angle-resolved photoemission spectroscopy, scanning tunneling microscopy, and first-principles calculations, the team found that hidden Fermi-surface nesting and associated CDW formation are the primary causes of a unique correlated metallic state with no signature of a Mott gap—in contrast to the gapped Mott-insulating nature of isostructural 1T-NbSe2.

“Our results highlighted the key role of underlying fermiology in characterizing the Mott phase of TMDs,” explains Sugawara. “They provided insights into the interplay between fermiology, electron correlation, and exotic quantum phases in 2D materials.”

The team continues to collaborate with other AIMR research groups to explore quantum phenomena and functionalities in monolayer TMDs that have yet to be discovered.

(Author: Patrick Han)


  1. Taguchi T., Sugawara K. Oka H., Kawakami T., Saruta Y., Kato T., Nakayama K., Souma S., Takahashi T., Fukumura T., and Sato T. Charge order with unusual star-of-David lattice in monolayer NbTe2 Physical Review B 107, L041105 (2023). | article

This research highlight has been approved by the authors of the original article and all information and data contained within has been provided by said authors.