We have studied the charge-density-wave (CDW) current conversion process in NbSe 3 wire structures of mesoscopic dimensions. A significant reduction of the phase-slip voltage associated with this conversion is observed if the spacing between current contacts is smaller than a few mm. This reduction cannot be explained with existing models of CDW current conversion. We suggest that single phase-slip events play a central role in micron-sized systems. The removal and addition of wave fronts may then become correlated in time. PACS numbers: 72.15.Nj, 71.45.Lr, The sliding motion of charge-density waves (CDWs) causes remarkable electrical transport phenomena in conductors with a chainlike structure [1]. At the interface between a metallic contact and a CDW conductor, this sliding must inevitably be accompanied by injection of charge into the CDW condensate. According to current understanding, conversion occurs through strain-induced phase-slip processes, analogous to phase slip in narrow superconducting channels [2] and superfluids [3].Sliding CDWs can be visualized as moving wave fronts that are coupled by elastic forces. The motion of these wave fronts causes a compression of the elastic CDW near one contact and a stretching near the other. Near contacts, phase slips can remove this strain [4,5]: a local amplitude defect is formed which grows across the whole sample cross section, so that one complete wave front is added or removed. The rate at which wave fronts are added is determined by the strain amplitude. The CDW strain profile has been studied by several techniques, including electromodulated infrared transmission [6] and synchrotron x rays [7,8].The displacement of the condensed electrons in the strained CDW causes an elastic force that is opposite the applied field. In transport measurements, this opposite force must be overcome, leading to an additional voltage between the current contacts. This phase-slip voltage V PS has been extensively studied for bulk crystals [9][10][11][12][13]. V PS depends only weakly on the charge-density-wave current I CDW , but increases strongly when temperature is lowered. Measurements on NbSe 3 crystals have shown that V PS is length independent for spacings larger than 20 mm [12]. First experiments on antidot arrays [14], however, have provided an indication that the conversion mechanism changes at submicron length scales.In this paper, we report the controlled study of phase slip on a mesoscopic scale. The measurements have been performed on small wires that were lithographically patterned into a NbSe 3 crystal. By changing contact pairs for current injection, the phase-slip voltage V PS has been determined as a function of current-contact spacing. A significant reduction of V PS is found for spacings smaller than 3 mm. We suggest that this reduction is a mesoscopic effect, related to the addition or removal of single CDW wave fronts.
We report on the thin-film fabrication of a charge-density wave (CDW) compound. Single-phase epitaxial films of the model CDW oxide Rb0.30MoO3 have been grown by pulsed-laser deposition. Detailed analyses show that the Rb0.30MoO3 films have μm-size grains with the CDW chains oriented parallel to the substrate. On SrTiO3 (510), the CDW chains align into a single direction within the film plane. The electrical resistance of the films demonstrates a CDW state below about 182 K. Structures patterned in films will permit unprecedented studies of phase-coherent CDW transport, as well as the exploration of devices based on CDWs.
We study sliding charge-density-wave ͑CDW͒ transport in mesoscopic wires of Rb 0.30 MoO 3 . The wires, with a width of 2 m and contact spacings down to 1 m, have been patterned into thin films by use of optical and electron-beam lithographic techniques. CDW sliding is evident from the nonlinear I(V) characteristics below the Peierls temperature. The threshold field E T for depinning of the CDW is 2-3 orders of magnitude higher than in bulk Rb 0.30 MoO 3 crystals, and increases exponentially with decreasing temperature down to about 50 K. At lower temperatures, the shape of the I(V) curves changes, and nonlinearity sets in at lower voltages. The observed transport properties are discussed in terms of CDW sliding and, at low temperatures, in terms of hopping of solitonlike excitations in the CDW lattice. ͓S0163-1829͑99͒16431-2͔ PHYSICAL REVIEW B 15 AUGUST 1999-II VOLUME 60, NUMBER 8 PRB 60 0163-1829/99/60͑8͒/5287͑8͒/$15.00 5287
Thin films of the model charge-density-wave compound Rb 0.30 MoO 3 ͑blue bronze͒ have been grown using pulsed-laser deposition. Films are single-phase Rb 0.30 MoO 3 , and consist of grains with typical sizes on the order of micrometers. The charge-density-wave chains are parallel to the film plane. Heteroepitaxial growth of Rb 0.30 MoO 3 is found on SrTiO 3 ͑100͒ substrates. The blue-bronze grains align their chains with the two principal axes of the square surface lattice of SrTiO 3 ͑100͒. Preferential orientation into a single direction can be obtained on SrTiO 3 ͑510͒. Measurements of the film resistance as a function of temperature show a transition to the charge-density-wave state near 182 K.
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