Regensburg 2010 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
O: Fachverband Oberflächenphysik
O 57: Surface dynamics II
O 57.5: Vortrag
Mittwoch, 24. März 2010, 16:00–16:15, H40
Ultrafast melting of orbital and charge order in magnetite — •Niko Pontius1, Torsten Kachel1, Hermann A. Dürr1, Christian Schüßler-Langeheine2, Bill Schlotter3, Martin Beye3, Florian Sorgenfrei3, Alexander Föhlisch1,3, and Wilfried Wurth3 — 1Helmholtz-Zentrum Berlin, BESSY II, 12489 Berlin — 2Physikalisches Institut, Universität zu Köln, 50937 Köln — 3Institut für Experimentalphysik, Universität Hamburg, 22761 Hamburg
At 120K magnetite (Fe3O4) undergoes a metal-to-insulator transition (the famous Verwey transition [1]) which is accompanied by a transition from a charge and orbital ordered state below the transition temperature to a state without electronic order [2]. Until today the question whether this transition is driven by the lattice or by electronic degrees of freedom remains unanswered. We studied this transition using time-resolved resonant soft x-ray diffraction (RSXD) at the free electron laser FLASH in Hamburg. Thus we get direct insight into the "melting" of charge and orbital order after selectively exciting the electronic system by an infrared fs-laser pulse from below the transition temperature. The experimental data reveal an unexpectedly slow melting on a time scale of ≈ 500 fs. This suggests that the melting process is limited by a rearrangement of the lattice. Moreover, by performing time-resolved spectroscopy on the RSXD-reflection peak at the oxygen K-edge we observe the narrowing of the band gap during the melting process.
[1] E.J.W. Verwey, Nature 144, 327-328 (1939)
[2] J. Schlappa et al. , Phys. Rev. Lett. 100, 026406 (2008)