Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 65: Time-resolved spectroscopies III
O 65.1: Vortrag
Freitag, 27. März 2009, 11:15–11:30, SCH A315
Transient electronic structure and melting of a charge density wave in TbTe3 — F. Schmitt1, P. S. Kirchmann2, •U. Bovensiepen2, R. G. Moore1,3, L. Rettig2, M. Krenz2, J.-H. Chu1, N. Ru1, L. Perfetti2, D. H. Lu3, M. Wolf2, and Z.-X. Shen1,3 — 1Stanford University, Department of Applied Physics, USA — 2Freie Universität Berlin, Fachbereich Physik, Germany — 3Stanford Synchrotron Radiation Laboratory, USA
Obtaining insight into cooperative effects is fascinating because, through self-coordination and collectivity, they can lead to instabilities with macroscopic impacts like phase transitions. The responsible interactions are of particular interest to understand these phenomena. We used femtosecond time- and angle-resolved photoelectron spectroscopy to analyze the electronic structure of the quasi-1D charge density wave (CDW) material TbTe3 which exhibits an energy gap at the Fermi surface along the nesting direction. A Te derived mode at 3.6 THz can be monitored by binding energy variations at all electron momenta, incident fluence F, and temperatures (T=100, 300K). A second mode at 2.3 THz is found only at low T and F, and exclusively at the Fermi surface. For higher F=2 mJ/cm2 we find after 100 fs a closing of the energy gap and a recurrence of quasi-free electron like dispersion crossing the Fermi surface. This indicates unambiguously an ultrafast melting of the CDW state and identifies the 2.3 THz mode as the CDW amplitude mode. We expect that the information which is accessible with trARPES will greatly enhance the understanding of materials exhibiting cooperative phenomena.