S. V. Zaitsev-Zotov

One-Dimensional Conduction in Charge-Density-Wave Nanowires

We report a systematic study of the transport properties of coupled one-dimensional metallic chains as a function of the number of parallel chains. When the number of parallel chains is less than 2000, the transport properties show power-law behavior on temperature and voltage, characteristic for one-dimensional systems.

Critical-state model for pinned charge-density waves: conditions and consequences of phase slip

Abstract In a quasi-one-dimensional conductor, phase slips can occur in pinned charge-density waves (CDWs) even under zero electric field. The conditioons for their onset and their subsequent evolution are discussed in detail. Phase slips perturb the CDW phase over the phase-coherence length, which increases exponentially with a decrease in temperature because of exponential growth of the CDW elastic modulus. At low temperatures, phase slips should evolute into static soliton-like formations (CDW dislocations). The proposed critical-state model is in agreement with our previous experiments.

Negative Resistance and Local Charge-Density-Wave Dynamics

Charge-density-wave (CDW) dynamics is studied on a submicron length scale in NbSe(3) and o-TaS(3). Regions of negative absolute resistance are observed in the CDW sliding regime at sufficiently low temperatures. The origin of the negative resistance is attributed to the different forces that the deformed CDW and quasiparticles feel: the force on the CDW is merely caused by a difference of the electric potentials, while the quasiparticle current is governed by a difference of the electrochemical potentials.

Gigahertz-range synchronization at room temperature and other features of charge-density wave transport in the quasi-one-dimensional conductor NbS3

Whiskers of the quasi-one-dimensional conductor NbS3, phase II, have been synthesized. The samples show two charge-density wave (CDW) states: below 360 and below 150 K. Both CDWs show sharp threshold fields and coherent transport revealed by ac-dc coupling, i.e., Shapiro steps. The thinnest samples (cross sections below 104 nm2) exhibit Shapiro steps for frequencies at least as high as 4 GHz at room temperature. The results indicate that, for each of the CDW states, only one Nb chain per unit cell participates in the CDW transport.

Transition to 1D conduction with decreasing thickness of the crystals of TaS3 and NbSe3 quasi-1D conductors

It is found that, with decreasing thickness of the crystals of TaS3 and NbSe3 quasi-1D conductors, the dependences of the conductivity of these crystals on temperature and electric field change from the form typical of bulk samples to a nearly power law behavior typical of 1D electron systems.

'Quantized' states of the charge-density wave in microcrystals of K 0.3 MoO 3

Quantization of electrons in solids can typically be observed in microscopic samples if the mean free path of the electrons exceeds the dimensions of the sample. A special case is a quasi one-dimensional metal, in which electrons condense into a collective state. This state, a charge-density wave (CDW), is a periodic modulation of both the lattice and electron density. Here, we demonstrate that samples of K(0.3)MoO(3), a typical CDW conductor, show jumps in conduction, regular in temperature. The jumps correspond to transitions between discrete states of the CDW and reveal the quantization of the wave vector of electrons near the Fermi vector. The effect involves both quantum and classical features of the CDW: the quantum condensate demonstrates modes, resembling those of a classical wave in a resonator. The analysis of the steps allows extremely precise studies of the CDW wave-vector variations and reveals new prospects for structural studies of electronic crystals and fine effects in their electronic states and lattice motions.

Charge-density waves physics revealed by photoconduction

The results of photoconduction study of the Peierls conductors are reviewed. The studied materials are quasi-one-dimensional conductors with the charge-density wave: K0.3MoO3, both monoclinic and orthorhombic TaS3 and also a semiconducting phase of NbS3 (phase I). Experimental methods, relaxation times, effects of illumination on linear and nonlinear charge transport, the electric-field effect on photoconduction and results of the spectral studies are described. We demonstrate, in particular, that a simple model of modulated energy gap slightly smoothed by fluctuations fits the available spectral data fairly well. The level of the fluctuations is surprisingly small and does not exceed a few percent of the optical energy gap value.

Convective terms and transversely driven charge-density waves

We derive the convective terms in the damping which determine the structure of the moving charge-density wave (CDW), and study the effect of a current flowing transverse to conducting chains on the CDW dynamics along the chains. In contrast to a recent prediction we find that the effect is orders of magnitude smaller, and that contributions from transverse currents of electron- and holelike quasiparticles to the force exerted on the CDW along the chains act in the opposite directions. We discuss recent experimental verification of the effect and demonstrate experimentally that geometry effects might mimic the transverse current effect.

Contribution of spontaneous phase slippage to linear and nonlinear conduction near the Peierls transition in thin samples of TaS3

In the Peierls state very thin samples of TaS3 ~cross-section area ;10 23 mm 2 ) are found to demonstrate smearing of the I-V curves near the threshold field. With approaching the Peierls transition temperature, T P , the smearing evolves into smooth growth of conductance from zero voltage interpreted by us as the contribution of fluctuations to the nonlinear conductance. We identify independently the fluctuation contribution to the linear conductance near T P . Both linear and nonlinear contributions depend on temperature with close activation energies ;(224)310 3 K and apparently reveal the same process. We reject creep of the continuous charge-density waves ~CDW’s! as the origin of this effect and show that it is spontaneous phase slippage that results in creep of the CDW. A model is proposed, accounting for both the linear and nonlinear parts of the fluctuation conduction up to T P .

STRONG-PINNING EFFECTS IN LOW-TEMPERATURE CREEP: CHARGE-DENSITY WAVES IN TAS3

Nonlinear conduction in the quasi-one dimensional conductor o-TaS_3 has been studied in the low-temperature region down to 30 mK. It was found that at temperatures below a few Kelvins the current-voltage (I-V) characteristics consist of several branches. The temperature evolution of the I-V curve proceeds through sequential freezing-out of the branches. The origin of each branch is attributed to a particular strong pinning impurity type. Similar behavior is expected for other physical systems with collective transport (spin-density waves, Wigner crystals, vortex lattices in type-II superconductors etc.) in the presence of strong pinning centers.