Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 31: Correlated Electrons: Low-Dimensional Systems -Materials 1
TT 31.2: Talk
Tuesday, March 12, 2013, 09:45–10:00, H41
Phonon Softening in the CDW Systems NbSe2 and TiSe2 — •Roland Hott1, Rolf Heid1, Klaus-Peter Bohnen1, Frank Weber1,2, Stephan Rosenkranz2, John-Paul Castellan1,2, Raymond Osborn2, Takeshi Egami3, Ayman Said4, and Dmitry Reznik1,5 — 1Karlsruhe Institute of Technology, Institute of Solid State Physics, P. B. 3640, D-76021 Karlsruhe, Germany — 2Materials Science Division, Argonne National Laboratory, Argonne, Illinois, 60439, USA — 3Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee, 37996, USA — 4Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, 60439, USA — 5Department of Physics, University of Colorado at Boulder, Boulder, Colorado, 80309, USA
We present new results on the soft-mode behaviour of phonons in the Charge Density Wave (CDW) systems NbSe2 and TiSe2. Our theoretical predictions from Density Functional Theory (DFT) based on ab-initio phonon calculations coincide with the CDW instability behaviour that we observed experimentally by means of high resolution Inelastic X-ray Scattering (IXS). While TiSe2 shows a rather sharp phonon anomaly at T = 190 K, the anomaly in NbSe2 at T = 33 K is much broader than expected for a Fermi surface nesting driven CDW instability. For NbSe2, we exclude Fermi surface nesting as main origin of the phonon softening. For TiSe2, the phonon softening seems to be well described within the framwork of DFT.