Dresden 2011 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 33: CE: Metal-Insulator Transition 1
TT 33.3: Vortrag
Mittwoch, 16. März 2011, 11:00–11:15, HSZ 105
The Verwey transition ultrafast: lattice and charge/orbital order go head-to-head — •N. Pontius1, C.-F. Chang2, T. Kachel1, C. Trabant1,3, M. Beye1, W. Schlotter3, S. de Jong3, F. Sorgenfrei4, R. Kukreja3, B. Bräuer3, M. Döhler2, S. Hossain3, C. Back3, A. Scherz3, D. Zhu3, J. Turner3, W.-S. Lee3, Y.-D. Chuang3, O. Krupin3, M. Buchholz2, P. Vogt2, W. Wurth4, A. Föhlisch1, H. A. Dürr3, and C. Schüßler-Langeheine1,3 — 1Helmholtz-Zentrum Berlin für Materialien und Energie GmbH — 2II. Physikalisches Institut, Universität zu Köln — 3SLAC National Accelerator Laboratory, USA — 4Institut für Experimentalphysik, Universität Hamburg
At 120K magnetite (Fe3O4) undergoes a metal-to-insulator transition, the Verwey transition. It is accompanied by a transition from a charge/orbital ordered state with a monoclinic symmetry to a high temperature cubic phase without electronic order. Until today the question whether this transition is mainly driven by the lattice or by electronic degrees of freedom remains unanswered.
Here we report on a time-resolved resonant soft x-ray diffraction experiment performed at the LCLS in Stanford, USA. We studied the structural and electronic response when the insulator-to-metal transition is induced by a fs laser pulse which selectively excites the electronic subsystem. Surprisingly, the data show that both, a change of lattice symmetry and the quenching of charge/orbital order occur on a sub 200fs timescale. Moreover, the measurements suggest the formation of a new transient phase, which has not been observed in equilibrium.