Condensed Matter Physics Seminar

Thursday, September 10, 1998, 3 p.m.
Room 1402, Physics Building
(Special time and place)

Phase Slips and Current Conversion in the Sliding State of a Charge Density Wave: The Impact of Spatially-Resolved X-Ray Studies

Serguei Brazovski

(Brookhaven National Laboratory)

Abstract: Plastic deformations and flows are currently on agenda in studies of Electronic Crystals: Charge/Spin Density Waves  or interface 2d Wigner Crystals, and of Vortex Lattices.  Dislocations are supposed to participate in depinning, in phase slips, in Narrow Band Noise generation, in contact structures. We review basic experimental and theoretical results and present new  studies* on a distribution of plastic deformations experienced by a sliding  CDW in the course of the conversion from the normal current to the collective one.  Recently high space resolution (down to 30 microns) X-rays measurements of the satellite position shift q have been performed on NbSe_3 [1]. For the first time q has been determined for the dc (as well as on pulsed) current and in a vicinity (even through) the injection contact.  We model a strong fall of q near contacts by equations for the intensive nucleation of dislocations via the CDW flow through the host defects.  Moreover a logarithmic time decay of q between pulses near contacts recovers a creep of pinned dislocations.  A small constant  persistent gradient of q in the middle half of the sample signifies that the conversion process is hindered when the pinning of dislocations overcomes the decreasing oversaturation of normal carriers.  We discuss both similarities and contradictions with earlier studies, especially by the Cornell group.

*In collaboration with the  Centre de Recherches sur les Tres Basses Temperatures of CNRS, Institute Laue-Langevin and European Synchrotron Radiation Facility - Grenoble, France.

[1]  H. Requardt et al., Phys. Rev. Lett. 80, 5631 (1998).

Host: Victor Yakovenko

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