1/f1/f noise in variable range hopping conduction

A mechanism of $1/f$ noise due to traps formed by impurities which have no neighbors with close energies in their vicinity is studied. Such traps slowly exchange electrons with the rest of conducting media. The concentration of traps and proportional to it $1/f$ noise exponentially grow with decreasing temperature in the variable range hopping regime. This theory provides smooth transition to the nearest neighbor hopping case where it predicts a very weak temperature dependence

Crossover from 2-dimensional to 1-dimensional collective pinning in NbSe3

We have fabricated NbSe$_3$ structures with widths comparable to the Fukuyama-Lee-Rice phase-coherence length. For samples already in the 2-dimensional pinning limit, we observe a crossover from 2-dimensional to 1-dimensional collective pinning when the crystal width is less than 1.6 $\mu$m, corresponding to the phase-coherence length in this direction. Our results show that surface pinning is negligible in our samples, and provide a means to probe the dynamics of single domains giving access to a new regime in charge-density wave physics.Comment: 4 pages, 2 figures, and 1 table. Accepted for publication in Physical Review

Distributed latent heat of the phase transitions in low-dimensional conductors

A simple consideration demonstrates that if the temperature of a second-order phase transition is suppressed by fluctuations, the dominating effect at the transition is a maximum, but not a jump of specific heat, $c_p$. One can attribute a certain value of latent heat to the transition; an estimate of the “latent heat” is proposed and compared with the behavior of $c_p$ and of thermal expansion at the Peierls and superconducting transitions

Effect of commensurability on the CDW deformation near a point contact

The results of investigation of normal metal(Cu, Au)-CDW (K$_{0.3}$MoO$_3$) point-contacts (PCs) in a wide range of temperature are reported. At ${\rm T}>80$ K the contact characteristics are adequately described by the semiconducting model of CDW. At $T<70$ K the $I-V$ characteristics of PCs Cu-K$_{0.3}$MoO$_3$ demonstrate a strain-compress asymmetry of the CDW. The observed behavior is likely to reveal the lock-in transition (incommensurate-commensurate) due to the electric-field induced strain of the CDW

Contributions of high-energy excitations to the linear and non-linear conduction near the Peierls transition

Very thin samples of TaS3 (cross-section area ∼ 10-3 µm2) are found to demonstrate smearing of the I-V curves near the threshold field in the Peierls state. With approaching the Peierls transition temperature, TP, the smearing evolves into smooth growth of conductance from zero voltage, interpreted by us as the contribution of fluctuations to the non-linear conductance. The fluctuation contribution to the linear conductance near TP is identified independently. Both linear and non-linear contributions depend on temperature with close activation energies ∼ (2 - 4) x 103 K and apparently reveal the same process. We reject creep of the continuous charge-density waves (CDW) as an origin of the effect and show that it is spontaneous phase slippage that results to creep of the CDW. A model is proposed accounting for both the linear and non-linear parts of the fluctuation conduction up to TP

Hysteresis in thermal expansion of the quasi 1-dimensional conductor TaS3_3: Coupling of the underlying and the electronic crystals

An interferometer-based setup for measurements of length of needle-like samples is developed, and thermal expansion of o-TaS$_3$ crystals is studied. Below the Peierls transition the temperature hysteresis of length $L$ is observed, the width of the hysteresis loop $\delta L/L$ being up to $5\times 10^{-5}$. Curiously, $L(T)$ changes so that it is in front of its equilibrium value. The hysteresis loop couples with that of conductivity. With lowering $T$ the charge-density waves' (CDW) elastic modulus grows and at 100 K becomes comparable with that of the lattice $Y_l$. The results justify the assumption about the strain dependence of the CDW wave vector and clarify the nature of the anomalies of $Y_l$ which occur on the CDW depinning. In particular, $Y_l$, is expected to show a strong drop in the static regime, if measured at sufficiently small sample elongation $(\delta L/L < 10^{ -5})$

Variable-range-hopping-like transverse conductivity of the quasi one-dimensional conductor TaS3_{3}

We report temperature dependence of transverse conductivity and its hysteresis in TaS$_3$. The results argue that the conductivity mechanism is variable-range hopping (VRH)

On the critical current for the charge density wave transport

We report transport measurements under very high current densities $j$, up to $10^8$ A/cm$^2$, of quasi-one-dimensional charge-density wave (CDW) conductors NbSe$_3$ and TaS$_3$. Above $j_0-10^1$ A/cm$^2$ the point contacts NbSe$_3$-NbSe$_3$ show a sharp singularity, and the TaS$_3$ nanosamples show metallic temperature dependence (positive d$R$/d$n$. We interpret both results as an evidence for the suppression of the Peierls gap 2A and development of the metallic state above $j_0$. Possible scenarios of the Peierls state destruction are discussed

The In-plane anisotropy of the hall anomaly in BSCCO whiskers

The Hall effect in single crystal BSCCO whiskers has been measured, with the current flowing along the a and b crystallographic directions. The ab-plane anisotropy of the Hall anomaly is found. The magnitude of the anomaly, as well as its anisotropy, are strongly affected by the structural defects. © 2005 Springer Science+Business Media, Inc