Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 100: Correlated Electrons: Other Materials
TT 100.6: Vortrag
Donnerstag, 19. März 2015, 16:15–16:30, H 3005
Instantaneous Band Gap Collapse in VO2 caused by Photocarrier Doping — •Marc Herzog1, Daniel Wegkamp1, Lede Xian2,3, Matteo Gatti3,4, Pierluigi Cudazzo2,3, Christina L. McGahan5, Robert E. Marvel5, Richard F. Haglund5, Angel Rubio1,2,3,6, Martin Wolf1, and Julia Stähler1 — 1Fritz-Haber-Institut der MPG, Berlin, Germany — 2Univ. del País Vasco, San Sebastian, Spain — 3European Theoretical Spectroscopy Facility (ETSF) — 4École Polytechnique, Palaiseau, France — 5Vanderbilt Univ., Nashville, Tennessee, USA — 6MPI for the Structure and Dynamics of Matter, Hamburg, Germany
We have investigated the controversially discussed mechanism of the insulator-to-metal transition (IMT) in VO2 by means of femtosecond time-resolved photoelectron spectroscopy (trPES). Our data show that photoexcitation transforms insulating monoclinic VO2 quasi-instantaneously into a metal without an 80 fs structural bottleneck for the photoinduced electronic phase transition. First-principles many-body perturbation theory calculations reveal an ultrahigh sensitivity of the VO2 band gap to variations of the dynamically screened Coulomb interaction thus supporting the fully electronically driven isostructural IMT indicated by our trPES results. We 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.