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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