Instantaneous Band Gap Collapse in Photoexcited Monoclinic VO2 due to Photocarrier Doping

Abstract : Using femtosecond time-resolved photoelectron spectroscopy we demonstrate that photoexcitation transforms monoclinic VO2 quasi-instantaneously into a metal. Thereby, we exclude an 80 fs structural bottleneck for the photoinduced electronic phase transition of VO2. First-principles many-body perturbation theory calculations reveal a high sensitivity of the VO2 band gap to variations of the dynamically screened Coulomb interaction, supporting a fully electronically driven isostructural insulatorto-metal transition. We thus conclude that the ultrafast band structure renormalization is caused by photoexcitation of carriers from localized V 3d valence states, strongly changing the screening before significant hot-carrier relaxation or ionic motion has occurred.
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Submitted on : Wednesday, February 4, 2015 - 3:38:59 PM
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Daniel Wegkamp, Marc Herzog, Lede Xian, Matteo Gatti, Pierluigi Cudazzo, et al.. Instantaneous Band Gap Collapse in Photoexcited Monoclinic VO2 due to Photocarrier Doping. Physical Review Letters, American Physical Society, 2014, 113, pp.216401. ⟨10.1103/PhysRevLett.113.216401⟩. ⟨hal-01113172⟩

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