ISSN:
1434-6036
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract A comprehensive study of the ac response properties of the classical stochastic model for sliding charge density waves (CDW) in quasi one-dimensional metals is made by numerically solving the associated Fokker-Planck equation. Above the conductivity threshold a noise mechanism is indispensable to give finite line widths to the resonances of the applied ac signal of frequency ω with the narrow band noise frequency ωOSC inherent in the model. In the present investigation a current noise of strengthT N proportional to the CDW current is used in the Fokker-Planck equation in order to model the broad band current noise frequently observed above threshold. The present model thus incorporates three characteristic frequency scales: ωOSC,T N ,and a “crossover” frequency ωOSC. Results are evaluated for the ac conductivity σ(ω;E 0,E ω) as function of frequency ω, dc bias electric fieldE 0 and ac signal field strengthE ω. ForE ω→0 the linear ac response is obtained by a separate treatment of the Fokker-Planck equation. The resonances near ω=ωOSC are studied in detail. Strong ac signals reduce the response at the fundamental resonance and lead to a harmonic interference structure nearnω=ωOSC. The overall agreement of the present results with recent measurements of the linear ac response is not good. In reality our results seem to be superimposed on a background not reproduced by the classical model with one “cross over” frequency. However, the peak in Im σ(ω;E 0,E ω=0) vs.E 0, when the narrow band noise frequency is near ω, is well reproduced. The spectral width of this peak which corresponds to the inductive dip in the susceptibility is studied as function of current noise strengthT N .The results stress the need for a complete Fokker-Planck treatment sinceT N is not simply related to the line width.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01323428
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