Coexisting Charge-Ordered States with Distinct Driving Mechanisms in Monolayer VSe2
Rebekah Chua ; Jans Henke ; Surabhi Saha ; Yuli Huang ; Jian Gou ; Xiaoyue He ; Tanmoy Das ; Jasper van Wezel ; Anjan Soumyanarayanan ; Andrew T.S. Wee
Jans Henke
Surabhi Saha
Tanmoy Das
Jasper van Wezel
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Abstract
Thinning crystalline materials to two dimensions (2D) creates a rich playground for electronic phases, including charge, spin, superconducting, and topological order. Bulk materials hosting charge density waves (CDWs), when reduced to ultrathin films, have shown CDW enhancement and tunability. However, charge order confined to only 2D remains elusive. Here we report a distinct charge ordered state emerging in the monolayer limit of 1T-VSe2. Systematic scanning tunneling microscopy experiments reveal that bilayer VSe2 largely retains the bulk electronic structure, hosting a tridirectional CDW. However, monolayer VSe2 ─consistently across distinct substrates─exhibits a dimensional crossover, hosting two CDWs with distinct wavelengths and transition temperatures. Electronic structure calculations reveal that while one CDW is bulk-like and arises from the well-known Peierls mechanism, the other is decidedly unconventional. The observed CDW-lattice decoupling and the emergence of a flat band suggest that the second CDW could arise from enhanced electron–electron interactions in the 2D limit. These findings establish monolayer–VSe2 as a host of coexisting charge orders with distinct origins, and enable the tailoring of electronic phenomena via emergent interactions in 2D materials.
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Source Title
ACS Nano
Publisher
American Chemical Society
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Date
2021-12-16
DOI
10.1021/acsnano.1c08304
Type
Article