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arXiv · 2212.12853

Charge order with unusual star-of-David lattice in monolayer NbTe2

Taiki Taguchi·Katsuaki Sugawara·Hirofumi Oka·Tappei Kawakami·Yasuaki Saruta·Takemi Kato·Kosuke Nakayama·Seigo Souma·Takashi Takahashi·Tomoteru Fukumura·Takafumi Sato
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Abstract

Interplay between fermiology and electron correlation is crucial for realizing exotic quantum phases. Transition-metal dichalcogenide (TMD) 1T-TaS2 has sparked a tremendous attention owing to its unique Mott-insulating phase coexisting with the charge-density wave (CDW). However, how the fermiology and electron correlation are associated with such properties has yet to be claried. Here we demonstrate that monolayer 1T-NbTe2 is a new class of two-dimensional TMD which has the star-of-David lattice similarly to bulk TaS2 and isostructural monolayer NbSe2, but exhibits a metallic ground state with an unusual lattice periodicity root19xroot19 characterized by the sparsely occupied star-of-David lattice. By using angle-resolved photoemission and scanning-tunneling spectroscopies in combination with first-principles band-structure calculations, we found that the hidden Fermi-surface nesting and associated CDW formation are a primary cause to realize this unique correlated metallic state with no signature of Mott gap. The present result points to a vital role of underlying fermiology to characterize the Mott phase of TMDs.

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Taiki Taguchi, Katsuaki Sugawara, Hirofumi Oka, Tappei Kawakami, Yasuaki Saruta, Takemi Kato, Kosuke Nakayama, Seigo Souma, Takashi Takahashi, Tomoteru Fukumura, Takafumi Sato. 2022-12-25. Charge order with unusual star-of-David lattice in monolayer NbTe2. https://doi.org/10.1103/physrevb.107.l041105

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