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Electronic structure and enhanced charge density wave order of monolayer VSe2

DOI: 10.1021/acs.nanolett.8b01649 DOI Help

Authors: Jiagui Feng (University of St Andrews) , Deepnarayan Biswas (University of St. Andrews; Suzhou Institute of Nano-Tech. and Nanobionics (SINANO)) , Akhil Rajan (University of St. Andrews) , Matthew D. Watson (University of St. Andrews) , Federico Mazzola (University of St. Andrews) , Oliver J. Clark (University of St. Andrews) , Kaycee Underwood (University of St. Andrews) , I. Markovic (University of St. Andrews; Max Planck Institute for Chemical Physics of Solids) , Martin Mclaren (University of St. Andrews) , Andrew Hunter (University of St. Andrews) , David M. Burn (Diamond Light Source) , Liam B. Duffy (University of Oxford; ISIS) , Sourabh Barua (University of Warwick) , Geetha Balakrishnan (University of Warwick) , Francois Bertran (Synchrotron SOLEIL) , Patrick Le Fevre (Synchrotron SOLEIL) , Timur Kim (Diamond Light Source) , Gerrit Van Der Laan (Diamond Light Source) , Thorsten Hesjedal (University of Oxford) , Peter Wahl (University of St. Andrews) , Phil D. C. King (University of St Andrews)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nano Letters

State: Published (Approved)
Published: June 2018
Diamond Proposal Number(s): 19771

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 diffraction. 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.

Journal Keywords: VSe2; charge-density wave; transition-metal dichalcogenide; monolayer

Subject Areas: Physics, Materials, Chemistry

Instruments: I05-ARPES

Other Facilities: SOLEIL; ESRF