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Dresden 2011 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 3: CE: Charge Density Wave \& Peierls Instability

TT 3.8: Vortrag

Montag, 14. März 2011, 12:30–12:45, HSZ 304

Electron Energy-Loss Spectroscopy on the Transition-Metal Dichalchogenide 2H-TaSe2 — •Andreas König1, Roman Schuster2, Helmuth Berger3, Martin Knupfer1, and Bernd Büchner11IFW Dresden, Institute for Solid State Research, P. O. Box 270116, D-01171 Dresden, Germany — 2Department of Physics, University of Fribourg, 1700 Fribourg, Switzerland — 3Insitut de Physique de la Matière Complexe, EPFL, CH-1051 Lausanne, Switzerland

2H-TaSe2 is one of the various polytypes of the transition-metal dichalchogenide (TMDC) TaSe2. It consists of hexagonal layers with weak interlayer van-der-Waals bonding. It shows phase transitions to a charge-density wave (CDW) and to a superconducting state. Although there is strong evidence for the competition of these two ordering effects as well as for a Peierls transition scenario for the origin of the CDW, a theoretical understanding of the mechanism leading to the phase transitions is still subject of discussions. What is already proved for 2H-TaSe2 and a few other TMDCs is a negative dispersion of the bulk plasmon 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. Furthermore, the slope of the plasmon dispersion is doping dependent. We performed Electron Energy-Loss Spectroscopy in transmission on thin films of 2H-TaSe2 for different potassium contents as well as for different temperatures above and below the CDW transition temperature to investigate the connection of the CDW phase transition to the plasmon dispersion.

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