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TT: Fachverband Tiefe Temperaturen
TT 22: Correlated Electrons: Low-dimensional Systems - Materials 1
TT 22.13: Vortrag
Mittwoch, 28. März 2012, 12:45–13:00, H 0104
Effect of Charge Order on the Plasmon Dispersion in Transition-Metal Dichalcogenides investigated by Electron Energy-Loss Spectroscopy — •Andreas König1, Jasper van Wezel2, Roman Schuster1, Martin Knupfer1, Helmuth Berger3, Jeroen van den Brink1, and Bernd Büchner1 — 1IFW Dresden, Institute for Solid State Research, P. O. Box 270116, D-01171 Dresden, Germany — 2Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA — 3Institut de Physique de la Matière Condensée, EPFL, CH-1015 Lausanne, Switzerland
2H-TaSe2 is one of the various polytypes of the transition-metal dichalchogenides (TMDC) that show a phase transition to a charge-density wave (CDW) and to a superconducting state. It is already proven for 2H-TaSe2 [1] and a few other TMDCs that they show a negative dispersion of the bulk plasmon energy in the normal state and an even larger bandwidth of this negative dispersion in the CDW state, which is altogether not a behavior of a common metal.
We discuss the connection of the susceptibility to a CDW phase and of the negative plasmon dispersion by applying Electron Energy-Loss Spectroscopy (EELS) measurements in transmission on thin films of 2H-TaSe2 as well as a semiclassical Ginzburg-Landau model [2]. The connection is further emphasized by intercalation experiments with potassium that show a suppression of the CDW as well as a change of slope of the plasmon dispersion.
[1] Schuster et al., Phys. Rev. B 79, 045134 (2009)
[2] van Wezel et al., Phys. Rev. Lett. 107, 176404 (2011)