J. Phys. I France 2 (1992) 111-120
Mesoscopic behaviour of the threshold voltage in ultra-small specimens of o-TaSS. V. Zaitsev-Zotov1, V. Ya. Pokrovskii1 and J. C. Gill2
1 Institute of Radio Engineering and Electronics, Academy of Sciences of the USSR, Marx Avenue 18, 103907 Moscow, U.S.S.R.
2 H. H. Wills Physics Laboratory, University of Bristol, Royal Fort, Tyndall Avenue, Bristol BS8 1TL, G.B.
(Received 1 August 1991, accepted 17 September 1991)
In very small ( cm 3) specimens of o-TaS 3, the threshold voltage for the onset of Frohlich conduction is found to vary irregularly with the temperature T. This behaviour is attributed to rearrangement of the charge-density wave (CDW) with respect to the pinning, as its wave-vector varies with T. It is consistent with weak, but not with strong, pinning by impurities. In sufficiently short ( m) specimens the variation of relative to its mean is substantially independent of specimen volume, as is expected when the dimensionality of the weak pinning is effectively zero. However, the value found for , where is the rms deviation of from , is smaller than for a rigid CDW whose coupling to impurities varies sinusoidally with phase. Possible causes of the discrepancy are an approach to strong pinning through local elastic distortion near pinning sites, a departure from zero-dimensional behaviour due to imperfect phase coherence in one transverse direction, and the pinning of widely-separated defects (dislocations) in the CDW structure.
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