J. Phys. IV France
Volume 12, Numéro 9, November 2002
Page(s) 39 - 42

J. Phys. IV France
12 (2002) Pr9-39
DOI: 10.1051/jp4:20020349

Studies of the dynamics in charge-density-wave systems using inelastic X-ray scattering with meV-energy-resolution

H. Requardt1, J.E. Lorenzo2, R. Danneau3, R. Currat3 and P. Monceau4

1  ESRF, BP. 220, 38043 Grenoble cedex, France
2  Laboratoire de Cristallographie, CNRS, BP. 166, 38042 Grenoble cedex, France
3  ILL, BP. 156, 38042 Grenoble cedex, France
4  CRTBT-CNRS, BP. 166, 38042 Grenoble cedex, France

We report measurements of the dynamics of the charge-density-wave systems K 0.3MoO 3 and NbSe 3 applying the quite recent technique of meV-resolution inelastic X-ray scattering (IXS). In K 0.3MoO 3, serving as a test-case with existing reference results from neutron scattering, the very steep slope of the phason dispersion has been reproduced by IXS together with a very good agreement for the observed "phason velocity": 26 km/sec (IXS) vs. 23 km/sec (neutrons). In NbSe 3, where IXS allows for dispersion studies on thin whiskers, the longitudinal acoustic and one transverse acoustic (TA 1) branch propagating along the NbSe 3-chain direction have been determined at room temperature. Low temperature TA 1-data have been taken around the upper-CDW satellite position (0, 0.241, 0) at temperatures down to below the upper Peierls transition (T $_{\rm p}$=145 K). The low temperature results indicate the absence of a Kohn anomaly, in contrast to the CDW-related dynamics observed in K 0.3MoO 3 and KCP, but similar as in (TaSe 4) 2I.

© EDP Sciences 2002