Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 21: Solids at Low Temperature - Poster Session
TT 21.20: Poster
Mittwoch, 28. März 2007, 14:00–17:45, Poster A
Low-temperature phonon dispersion in 2H-NbSe2 by inelastic neutron scattering and ab-inito calculations — •Karin Schmalzl1,2, Arno Hiess2, Dieter Strauch3, and Helmuth Berger4 — 1Forschungszentrum Juelich, 52425 Juelich, Germany — 2Institut Laue Langevin, 38042 Grenoble, France — 3Universitaet Regensburg, 93040 Regensburg, Germany — 4Ecole Politechnique Federale de Lausanne, 1015 Lausanne, Switzerland
2H-NbSe2 belongs to the group of quasi-two-dimensional layered transition metal dichalcogenides. The 2H polytypes consist of stacked hexagonal planes. Several interesting properties like superconductivity (Tc ≈ 7 K), anisotropic electrical properties, incommensurate charge-density wave (CDW) instability ( TCDW ≈ 35 K), and very anisotropic k-dependent electron-phonon coupling are found. Also, many lattice properties like thermal expansion, sound velocity, etc. are very anisotropic. Superconductivity and CDW order coexist at low T.
It is suspected that in these systems there is a connection between the charge-density wave, a strongly anisotropic electron-phonon coupling, lattice distortion, and phonon anomalies. The CDW is slightly incommensurate with a wavevector near 1/3(1,0,0).
We have now investigated the low-frequency branches of the phonon dispersion at 50 K in frequency, width, and intensity, also along non-main-symmetry directions around the phonon wavector q = 1/3(1,0,0) by inelastic neutron scattering. The experiments are accompanied by ab-initio calculations.