H. Requardt et al., Space- and time-resolved X-ray diffraction from pinned and sliding charge-density-waves in NbSe3, J PHYS IV, 9(P10), 1999, pp. 133-137
We have determined the spatial distribution of the local charge-density-wav
e (CDW) strain in the sliding state of NbSe3. The strain is measured by mon
itoring the spatially-varying shift q(x) of the CDW satellite wave vector b
etween current contacts. Experiments were carried out at T = 90 K in the up
per CDW state using high spatial resolution (30-50 mu m) X-ray diffraction.
Applying direct currents about twice the threshold value, we observe a ste
ep exponential decrease of the shift within a few hundred microns from the
contact followed by a linear variation of q in the central section of the s
ample. This latter regime is attributed to transverse pinning of the CDW di
slocation loops (DL), while the exponential regime is controlled by the fin
ite DL nucleation rate. Additional to these data in the stationary state of
the sliding CDW, we investigated the relaxation of the CDW strain q(ij upo
n switching off the current (T = 75 K). Using time-resolved high-spatial re
solution X-ray diffraction, we observe at 800 mu m from the electrode a dec
ay law of the stretched exponential type: q(t) = q(0) exp(-(t/tau)(mu))) wi
th tau = 283 ms and mu = 0.37.