Electronic structure and enhanced charge-density wave order of monolayer VSe2

Jiagui Feng, Deepnarayan Biswas, Rajan Akhil, Matthew D. Watson, Federico Mazzola, Oliver Jon Clark, Kaycee Underwood, Igor Markovic, Martin McLaren, Andrew Hunter, David M. Burn, Liam B. Duffy, Sourabh Barua, Geetha Balakrishnan, François Bertran, Patrick Le Fevre, Timur K. Kim, Gerrit van der Laan, Thorsten Hesjedal, Peter WahlPhilip D C. King

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Abstract

How the interacting electronic states and phases of layered transition-metal dichalcogenides evolve when thinned to the single-layer limit is a key open question in the study of two-dimensional materials. Here, we use angle-resolved photoemission to investigate the electronic structure of monolayer VSe2 grown on bi-layer graphene/SiC. While the global electronic structure is similar to that of bulk VSe2, we show that, for the monolayer, pronounced energy gaps develop over the entire Fermi surface with decreasing temperature below Tc = 140 ± 5 K, concomitant with the emergence of charge-order superstructures evident in low-energy electron diraction. These observations point to a charge-density wave instability in the monolayer which is strongly enhanced over that of the bulk. Moreover, our measurements of both the electronic structure and of x-ray magnetic circular dichroism reveal no signatures of a ferromagnetic ordering, in contrast to the results of a recent experimental study as well as expectations from density-functional theory. Our study thus points to a delicate balance that can be realised between competing interacting states and phases in monolayer transition-metal dichalcogenides.
Original languageEnglish
Pages (from-to)4493-4499
Number of pages7
JournalNano Letters
Volume18
Issue number7
Early online date18 Jun 2018
DOIs
Publication statusPublished - 11 Jul 2018

Keywords

  • VSe2
  • Charge-density wave
  • Transition-metal dichalcogenide
  • Monolayer

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