Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 77: Focus Session: Structural Dynamics in Nanoscale Materials Probed by Ultrashort Electron Pulses
O 77.1: Topical Talk
Donnerstag, 19. März 2015, 10:30–11:00, MA 005
Photoinduced phase transitions in vanadium dioxide revealed by ultrafast electron diffraction and broadband spectroscopy — •Bradley Siwick1, Vance Morrison1, Robert Chatelain1, Kunal Tiwari1, Ali Hendaoui2, Andrew Bruhacs1, and Mohamed Chaker2 — 1Departments of Physics and Chemistry, Center for the Physics of Materials, McGill University, Montreal, Canada — 2Institut National de la Recherche Scientifique, Centre Énergie Matériaux et Télécommunications, Varennes, Canada
The complex interplay between strong electron-electron correlations and structural distortions is thought to determine the electronic properties of many oxides, but the respective role of the two contributions is often extremely difficult to determine. Vanadium dioxide is a particularly notorious example. We will report on combined radio-frequency compressed ultrafast electron diffraction (RF-UED) and infrared transmissivity experiments in which we directly watch and separate the lattice and charge density reorganizations that are associated with the optically induced semiconductor-to-metal transition in vanadium dioxide. These studies have uncovered a previously unreported photoinduced transition to a metastable intermediate state with the periodic lattice distortion characteristic of the insulator intact, but differing by a 1D rearrangement of charge density along the octahedrally coordinated vanadium dimer chains and a transition to metal-like mid IR optical properties. The results demonstrate that UED is capable of following details of both lattice and electronic structural dynamics on the ultrafast timescale.