Coexisting charge-ordered states with distinct driving mechanisms in monolayer VSe${}_2$

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 $1T$-VSe${}_2$. Systematic scanning tunneling microscopy experiments reveal that bilayer VSe${}_2$ largely retains the bulk electronic structure, hosting a tri-directional CDW. However, monolayer VSe${}_2$ -- 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 new CDW could arise from enhanced electron-electron interactions in the 2D limit. These findings establish monolayer-VSe${}_2$ as a host of coexisting charge orders with distinct origins, and enable the tailoring of electronic phenomena via emergent interactions in 2D materials.

8 pages, 5 figures

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Cited by in corpus (5)

• Novel 2D vanadium sulphides: synthesis, atomic structure engineering and charge density waves
• Quantum Monte Carlo and density functional theory study of strain and magnetism in 2D 1T-VSe${}_2$ with charge density wave states
• Generating Two-dimensional Ferromagnetic Charge Density Waves via External Fields
• Anomalous amplitude mode dynamics below the expected charge-density-wave transition in 1$T$-VSe${}_2$
• Incommensurate charge density wave on multiband intermetallic systems exhibiting competing orders