Journal
NANO LETTERS
Volume 21, Issue 5, Pages 1968-1975Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.0c04409
Keywords
Single-layer VSe2; metal-insulator transition; charge density wave; ultrafast dynamics; time- and angle-resolved photoemission spectroscopy
Categories
Funding
- VILLUM FONDEN [15375]
- Centre of Excellence for Dirac Materials [11744]
- Danish Council for Independent Research, Natural Sciences, under the Sapere Aude program [DFF-9064-00057B, DFF-6108-00409]
- Aarhus University Research Foundation
- National Research Foundation (NRF) - Korean government [NRF-2020R1A2C200373211, 2019K1A3A7A09033389]
- International Max Planck Research School for Chemistry and Physics of Quantum Materials (IMPRS-CPQM)
- Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy [DE-AC02-05CH11231]
- STFC
- National Research Foundation of Korea [2019K1A3A7A09033389] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
- EPSRC [EP/L017008/1] Funding Source: UKRI
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The study reveals that the interaction between electronic and lattice degrees of freedom in single-layer VSe2 leads to the charge density wave transition. In the insulating state, a light-induced closure of the energy gap was observed.
The transition-metal dichalcogenide VSe2 exhibits an increased charge density wave transition temperature and an emerging insulating phase when thinned to a single layer. Here, we investigate the interplay of electronic and lattice degrees of freedom that underpin these phases in single-layer VSe2 using ultrafast pump-probe photoemission spectroscopy. In the insulating state, we observe a light-induced closure of the energy gap, which we disentangle from the ensuing hot carrier dynamics by fitting a model spectral function to the time-dependent photoemission intensity. This procedure leads to an estimated time scale of 480 fs for the closure of the gap, which suggests that the phase transition in single-layer VSe2 is driven by electron-lattice interactions rather than by Mott-like electronic effects. The ultrafast optical switching of these interactions in SL VSe2 demonstrates the potential for controlling phase transitions in 2D materials with light.
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