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We present key issues of related phenomenons of the Ferroelectricity and the Charge Disproportionation in organic metals. In (TMTTF_2X the dielectric susceptibility demonstrates clear cases of the ferroelectric and anti-ferroelectric phase transitions. Both the susceptibility and the conductivity prove independence and occasional coexistence of "structurless" ferroelectric transitions and usual "anionic" ones. Their sequence gives access to physics of three types of solitons emerging upon cooling via several steps of symmetry breaking. The theory invokes a concept of the Combined Mott-Hubbard State which focuses upon weak processes of electronic Umklapp scattering coming from both the build-in nonequivalence of bonds and the spontaneous one of sites. We propose that the charge ordering in its form of the ferroelectricity exists hiddenly even in the Se subfamily (TMTSF)_2X, giving rise to the unexplained yet low frequency optical peak and the enhanced pseudogap., Comment: Proceedings of the ICSM 2002

We study the scaling properties of the clusters grown by the Wolff algorithm on seven different Sierpinski-type fractals of Hausdorff dimension $1 < d_f \le 3$ in the framework of the Ising model. The mean absolute value of the surface energy of Wolff cluster follows a power law with respect to the lattice size. Moreover, we investigate the probability density distribution of the surface energy of Wolff cluster and are able to establish a new scaling relation. It enables us to introduce a new exponent associated to the surface energy of Wolff cluster. Finally, this new exponent is linked to a dynamical exponent via an inequality., Comment: 12 pages, 3 figures. To appear in PRB

We study the critical behavior of the 3-state Potts model, where the spins are located at the centers of the occupied squares of the deterministic Sierpinski carpet. A finite-size scaling analysis is performed from Monte Carlo simulations, for a Hausdorff dimension $d_{f}$ $\simeq 1.8928$. The phase transition is shown to be a second order one. The maxima of the susceptibility of the order parameter follow a power law in a very reliable way, which enables us to calculate the ratio of the exponents $\gamma /\nu$. We find that the scaling corrections affect the behavior of most of the thermodynamical quantities. However, the sequence of intersection points extracted from the Binder's cumulant provides bounds for the critical temperature. We are able to give the bounds for the exponent $1/\nu$ as well as for the ratio of the exponents $\beta/\nu$, which are compatible with the results calculated from the hyperscaling relation., Comment: 13 pages, 4 figures

We perform a Monte Carlo Renormalization Group analysis of the critical behavior of the ferromagnetic Ising model on a Sierpi\'nski fractal with Hausdorff dimension $d_f\simeq 1.8928$. This method is shown to be relevant to the calculation of the critical temperature $T_c$ and the magnetic eigen-exponent $y_h$ on such structures. On the other hand, scaling corrections hinder the calculation of the temperature eigen-exponent $y_t$. At last, the results are shown to be consistent with a finite size scaling analysis., Comment: 16 pages, 7 figures

We present the first low-temperature thermodynamic investigation of the controlled physisorption of He$^{4}$ gas in carbon single-wall nanotube (SWNT) samples. The vibrational specific heat measured between 100 mK and 6 K demonstrates an extreme sensitivity to outgassing conditions. For bundles with a few number of NTs the extra contribution to the specific heat, C$_{ads}$, originating from adsorbed He$^{4}$ at very low density displays 1D behavior, typical for He atoms localized within linear channels as grooves and interstitials, for the first time evidenced. For larger bundles, C$_{ads}$ recovers the 2D behaviour akin to the case of He$^{4}$ films on planar substrates (grafoil)., Comment: 4 pages, 3 figures, submitted to Phys. Rev. Lett

Magnetoresistance in long correlated nanowires of degenerate semiconductor InSb in asbestos matrix (wire diameter of around 5 nm, length 0.1 - 1 mm) is studied over temperature range 2.3 - 300 K. At zero magnetic field the electric conduction $G$ and the current-voltage characteristics of such wires obey the power laws $G\propto T^\alpha$, $I\propto V^\beta$, expected for one-dimensional electron systems. The effect of magnetic field corresponds to a 20% growth of the exponents $\alpha$, $\beta$ at H=10 T. The observed magnetoresistance is caused by the magnetic-field-induced breaking of the spin-charge separation and represents a novel mechanism of magnetoresistance., Comment: To be published in JETP Letters, vol. 77 (2003)

Measurements of the magnetic susceptibility and its anisotropy in the quasi-one-dimensional system o-TaS_{3} in its low-T charge density wave (CDW) ground state are reported. Both sets of data reveal below 40 K an extra paramagnetic contribution obeying a power-law temperature dependence \chi(T)=AT^{-0.7}. The fact that the extra term measured previously in specific heat in zero field, ascribed to low-energy CDW excitations, also follows a power law C_{LEE}(0,T)=CT^{0.3}, strongly revives the case of random exchange spin chains. Introduced impurities (0.5% Nb) only increase the amplitude C, but do not change essentially the exponent. Within the two-level system (TLS) model, we estimate from the amplitudes A and C that there is one TLS with a spin s=1/2 localized on the chain at the lattice site per cca 900 Ta atoms. We discuss the possibility that it is the charge frozen within a soliton-network below the glass transition T_{g}~40 K determined recently in this system., Comment: 7 pages, 3 figures, submitted to Europhysics Letters

Magnetoresistance measurements have been carried out along the highly conducting a axis in the FISDW phase of hydrogened and deuterated (TMTSF)$_2$ClO$_4$ for various cooling rates through the anion ordering temperature. With increasing the cooling rate, a) the high field phase boundary $\beta_{\rm {HI}}$, observed at 27 T in hydrogened samples for slowly cooled, is shifted towards a lower field, b) the last semimetallic SDW phase below $\beta_{\rm {HI}}$ is suppressed, and c) the FISDW insulating phase above $\beta_{\rm {HI}}$ is enhanced in both salts. The cooling rate dependence of the FISDW transition and of $\beta_{\rm {HI}}$ in both salts can be explained by taking into account the peculiar SDW nesting vector stabilized by the dimerized gap due to anion ordering., Comment: 6pages,6figures(EPS), accepted for publication in PRB

Characteristic features of transverse transport along the $a^*$ axis in the NbSe$_3$ charge-density-wave conductor are studied. At low temperatures, the $I$-$V$ characteristics of both layered structures and NbSe$_3$-NbSe$_3$ point contacts exhibit a strong peak of dynamic conductivity at zero bias voltage. In addition, the $I$-$V$ characteristics of layered structures exhibit a series of peaks that occur at voltages equal to multiples of the double Peierls gap. The conductivity behavior observed in the experiment resembles that reported for the interlayer tunneling in Bi-2212 high-$T_c$ superconductors. The conductivity peak at zero bias is explained using the model of almost coherent interlayer tunneling of the charge carriers that are not condensed in the charge density wave., Comment: 11 pages including 5 figures

We show that the dynamics of disordered charge density waves (CDWs) and spin density waves (SDWs) is a collective phenomenon. The very low temperature specific heat relaxation experiments are characterized by: (i) ``interrupted'' ageing (meaning that there is a maximal relaxation time); and (ii) a broad power-law spectrum of relaxation times which is the signature of a collective phenomenon. We propose a random energy model that can reproduce these two observations and from which it is possible to obtain an estimate of the glass cross-over temperature (typically $T_g \simeq 100 - 200$ mK). The broad relaxation time spectrum can also be obtained from the solutions of two microscopic models involving randomly distributed solitons. The collective behavior is similar to domain growth dynamics in the presence of disorder and can be described by the dynamical renormalization group that was proposed recently for the one dimensional random field Ising model [D.S. Fisher, P. Le Doussal and C. Monthus, Phys. Rev. Lett. {\bf 80}, 3539 (1998)]. The typical relaxation time scales like $\tau^{\rm typ} \sim \tau_0 \exp{(T_g/T)}$. The glass cross-over temperature $T_g$ related to correlations among solitons is equal to the average energy barrier and scales like $T_g \sim 2 x \xi_0 \Delta$. $x$ is the concentration of defects, $\xi_0$ the correlation length of the CDW or SDW and $\Delta$ the charge or spin gap., Comment: 20 pages, 16 figures

We report transport measurements under very high current densities $j$, up to $\sim10^8$~A/cm$^2$, of quasi-one-dimensional charge-density wave (CDW) conductors NbSe$_3$ and TaS$_3$. Joule heating has been minimized by using a point-contact configuration or by measuring samples with extremely small cross-sections. Above $j_c \approx 10^7$~A/cm$^2$ we find evidence for suppression of the Peierls gap and development of the metallic state. The critical CDW velocity corresponding with $j_0$ is comparable with the sound velocity, and with $\Delta/ \hbar k_F$ ($k_F$ is the Fermi wave vector), which corresponds to the depairing current. Possible scenarios of the Peierls state destruction are discussed., Comment: 5pages, 5 figures

This paper is a direct illustration of a construction of coherent states which has been recently proposed by two of us (JPG and JK). We have chosen the example of a particle trapped in an infinite square-well and also in P\"oschl-Teller potentials of the trigonometric type. In the construction of the corresponding coherent states, we take advantage of the simplicity of the solutions, which ultimately stems from the fact they share a common SU(1,1) symmetry \`a la Barut--Girardello. Many properties of these states are then studied, both from mathematical and from physical points of view., Comment: 48 pages, 21 figures

We present experimental evidences for a ferro-electric transition in the family of quasi one- dimensional conductors (TMTTF)2X. We interpret this new transition in the frame of the combined Mott-Hubbard state taking into account the double action of the spontaneous charge disproportionation on the TMTTF molecular stacks and of the X anionic potentials.

Using high-resolution X-ray scattering techniques, we measure the variation, q(x), of the position in reciprocal space of the CDW satellite, in the sliding state, along the length of NbSe_3 whiskers. We show that structural defects and intentionally X-ray radiation-damaged regions increase locally the CDW pinning force, and induce CDW phase distortions which are consistent with those observed near contacts. Using the semi-microscopic model from Brazovskii describing the normal-condensed carrier conversion, with spatially varying parameters, we account for the experimental spatial dependence of the CDW phase gradient near both types of defects.

Conductivity and permittivity of the quasi-one-dimensionsional organic transfer salt (TMTTF)2PF6 have been measured at low frequencies (10^3-10^7 Hz) between room temperature down to below the temperature of transition into the spin-Peierls state. We interpret the huge real part of the dielectric permittivity (up to 10^6) in the localized state as the realization in this compound of a charge ordered state of Wigner crystal type due to long range Coulomb interaction., Comment: 11 pages, 3 .eps figures

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 hole-like 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., Comment: RevTeX, 9 pages, 1 figure, accepted for publications in PRL

Long nanowires of degenerate semiconductor InSb in asbestos matrix (wire diameter is around 50 \AA, length 0.1 - 1 mm) were prepared. Electrical conduction of these nanowires is studied over a temperature range 1.5 - 350 K. It is found that a zero-field electrical conduction is a power function of the temperature $G\propto T^\alpha$ with the typical exponent $\alpha \approx 4$. Current-voltage characteristics of such nanowires are found to be nonlinear and at sufficiently low temperatures follows the power law $I\propto V^\beta$. It is shown that the electrical conduction of these nanowires cannot be accounted for in terms of ordinary single-electron theories and exhibits features expected for impure Luttinger liquid. For a simple approximation of impure LL as a pure one broken into drops by weak links, the estimated weak-link density is around $10^3-10^4$ per cm., Comment: 5 pages, 2 figures

The temperature dependence of the low-temperature dielectric response is studied in o-TaS$_3$ samples doped by Nb, Se, and Ni and for nominally pure ones. It is found, that the low-temperature dielectric constant depends anomalously on doping and is higher for doped crystals, whereas the temperature dependence of the characteristic time of all samples follows the activation law with nearly the same activation energy $\sim 400$ K (T>20 K). The observed behaviour is inconsistent with all available explanations of the low-temperature dielectric anomaly., Comment: RevTex, 12 pages, epsf, 2 postscript Figures. Accepted for publication in Physics Letters A

We demonstrate for the first time that a periodic array of submicrometer holes (antidots) can be patterned into thin single NbSe3 crystals. We report on the study of charge density wave (CDW) transport of the network of mesoscopic units between antidots. Size of the elementary unit can be as small as 0.5 micron along the chain axis and (0.2 micron) x (0.3 micron) in cross section. We observe size effects for Ohmic residual resistance and in CDW transport current-voltage characteristics in submicronic networks., Comment: 4 pages with 1 table and 10 figures. Submitted to European Physical Journal

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., Comment: 11 pages, 3 ps figures, Revtex, To be published in Phys. Rev. Letters (1997)