The time-dependent Ginzburg-Landau approach is used to investigate nonlinear response of a strongly type-II superconductor. The dissipation takes a form of the flux flow which is quantitatively studied beyond linear response. Thermal fluctuations, represented by the Langevin white noise, are assumed to be strong enough to melt the Abrikosov vortex lattice created by the magnetic field into a moving vortex liquid and marginalize the effects of the vortex pinning by inhomogeneities. The layered structure of the superconductor is accounted for by means of the Lawrence-Doniach model. The nonlinear interaction term in dynamics is treated within Gaussian approximation and we go beyond the often used lowest Landau level approximation to treat arbitrary magnetic fields. The I-V curve is calculated for arbitrary temperature and the results are compared to experimental data on high-$T_{c}$ superconductor YBa$_{2}$Cu$_{3}$O$%_{7-δ}$.
Thermal fluctuation conductivity for a layered superconductor in perpendicular magnetic field is treated in the frame of the self-consistent Hartree approximation for an arbitrarily strong in-plane electric field. The simultaneous application of the two fields results in a slightly stronger suppression of the superconducting fluctuations, compared to the case when the fields are applied individually.
The excess Hall conductivity, resulting from thermal fluctuations of the superconducting order parameter, is calculated for a layered superconductor for an arbitrarily strong in-plane electric field and a perpendicular magnetic field in the frame of the time-dependent Ginzburg-Landau theory. The fluctuation Hall conductivity is suppressed in high electric fields much stronger than the longitudinal one. For high-temperature superconductors we predict a pronounced non-Ohmic behavior of the excess Hall effect near the critical temperature in moderate magnetic fields and electric fields of the ord…
The time-dependent Ginzburg-Landau approach is used to calculate the complex fluctuation conductivity in layered type-II superconductor under magnetic field. Layered structure of the superconductor is accounted for by means of the Lawrence-Doniach model, while the nonlinear interaction term in dynamics is treated within self-consistent Gaussian approximation. In high-$T_{c}$ materials, large portion of the $H-T$ diagram belongs to vortex liquid phase. The expressions summing contributions of all the Landau levels are presented in explicit form which are applicable essentially to the whole phas…
We demonstrate the electrical and thermal transport of layered bismuth-based sulfide EuBiS2F from 300 to 623 K. Although significant hybridization between Eu 4f and Bi 6p electrons was reported previously, the carrier transport of the compound is similar to those of F-doped LaBiS2O, at least above 300 K. The lattice thermal conductivity is lower than that of isostructural SrBiS2F, which is attributed to heavier atomic mass of Eu ions.
The non-Ohmic effect of a high electric field on the out-of-plane magneto-conductivity of a layered superconductor near the superconducting transition is studied in the frame of the Langevin approach to the time-dependent Ginzburg-Landau equation. The transverse fluctuation conductivity is computed in the self-consistent Hartree approximation for an arbitrarily strong electric field and a magnetic field perpendicular to the layers. Our results indicate that high electric fields can be effectively used to suppress the out-of-plane fluctuation conductivity in high-temperature superconductors and…
The paraconductivity, originating from critical superconducting order-parameter fluctuations in the vicinity of the critical temperature in a layered superconductor is calculated in the frame of the self-consistent Hartree approximation, for an arbitrarily strong electric field and zero magnetic field. The paraconductivity diverges less steep towards the critical temperature in the Hartree approximation than in the Gaussian one and it shows a distinctly enhanced variation with the electric field. Our results indicate that high electric fields can be effectively used to suppress order-parameter…
A simplified model of c axis transport in the high T_c superconductors is presented. Expressions are found for the c axis optical conductivity, the d.c. resistivity, and the c axis penetration depth. Within the framework of this model, the pseudogap in the optical conductivity arises naturally as a result of the layered band structure of the high T_c materials. We discuss the occurence of the pseudogap in terms of three parameters: a band gap Delta_{ps}, a temperature dependent scattering rate Gamma(T), and the strength of the interlayer coupling t_{perp}. We are also able to find analytic exp…
In this paper, we discuss the c axis optical conductivity Re [sigma_c(omega)] in the high T_c superconductors, in the superconducting state. The basic premise of this work is that electrons travelling along the c axis between adjacent CuO_2 layers must pass through several intervening layers. In earlier work we found that, for weak inter-layer coupling, it is preferable for electrons to travel along the c axis by making a series of interband transitions rather than to stay within a single (and very narrow) band. Moreover, we found that many of the properties of the normal state optical conduct…
The criterion for the maximum incoherent conductivity $σ_{c,max}$ in the anisotropic system is shown to be $σ_{c,max} σ_{ab}=C (e^2/h)^2 n_{2D}$, where $n_{2D}$ is the two-dimensional electron density, and $C$ is a numerical constant of order one. A model of c-axis interlayer conductivity of layered system in the incoherent regime is developed. The temperature dependence of the c-axis conductivity is derived to be $σ_c (T) \sim T^α$, where $α$ is determined by the effective strength of the interplane voltage fluctuations. The ``pseudogap'' phenomenon of suppressed interplane conductivity at lo…
We show that the resistive anisotropy of an anisotropic medium is determined by the ratio of the phase coherence lengths. In layered crystals in which the interlayer transport is incoherent, the out-of-plane phase coherence length is fixed and temperature independent. This leads to a temperature dependent resistive anisotropy and to the coexistence of metallic in-plane and non-metallic out-of-plane conductivities. Our approach provides a description of the c-axis conductivity in the highly nonclassical regime, characteristic of layered cuprates.
Distinctive normal-state properties of cuprate superconductors follow from their charge carriers forming a large-bipolaron liquid. The very weak scattering of the slow-moving heavy-massed excitations of the liquid by acoustic phonons yields a scattering rate that is less than the Debye frequency. The moderate liquid mobility, greater than 1 cm2/V-sec at 300 K, results as the weak scattering of the liquid compensates for its large mass. In resolution of a long-standing dilemma, the dc resistivity resulting from scattering by acoustic phonons remains nearly proportional to temperature to well be…
Renormalization of the Coulomb interaction in layered metals results in a strongly anisotropic plasma mode with low frequencies for small components of wave vector in the in-plane direction. Interaction of electrons with this mode was found to lead to an incoherent contribution to the electron spectral density which spreads up to large energies. In the superconducting state this reproduces the peak-dip-hump feature similar to that observed in layered high-T$_c$ superconductors. The incoherent part of the spectral density and plasmon-assisted electron transitions provide mechanisms for nearly l…
The angle-dependent interlayer magnetoresistance of the layered organic metal $α$-(BEDT-TTF)$_2$KHg(SCN)$_4$ is found to undergo a dramatic change from the classical conventional behavior at low magnetic fields to an anomalous one at high fields. This field-induced crossover and its dependence on the sample purity and temperature imply the existence of two parallel channels in the interlayer transport: a classical Boltzmann conductivity $σ_{c}$ and an incoherent channel $σ_{i}$. We propose a simple model for $σ_{i}$ explaining its metallic temperature dependence and low sensitivity to the inpl…
We present a theory of the Josephson effect in a twofold-tilted Josephson junction made by d-wave anisotropic layered superconductors. We find the appearance of an intrinsic electrical resistance that arises from the misalignment of the superconductive planes (the CuO_2 planes in YBCO) in the two electrodes. This intrinsic contribution to the tunnel barrier has several non-trivial consequences. The result is relevant for understanding the electric transport properties of [100] tilt and [100] tilt-tilt Josephson junctions based on d-wave superconductors.
The thermal fluctuations of the electric field between the CuO_2 planes of layered cuprates are considered as an origin of the electrical resistivity. The model evaluation employs a set of separate plane capacitors each having area equal to the squared in-plane lattice constant a_0^2. It is shown that the scattering of charge carriers by the fluctuation of electric charge in the conducting CuO_2 planes gives rise to the in-plane electrical resistivity rho_ab. Such a mechanism can be viewed as an analog of the Rayleigh's blue-sky law---the charge carriers are scattered by thermal fluctuations o…
Using the Hubbard model on a 1D lattice and the "memory function" approach,we have calculated the electrical conductivity of a 1D system of correlated electrons on a lattice. We have determined the temperature and frequency profiles of the conductivity. Effects of changes of the band filling on the conductivity were also briefly discussed.The results were compared with experimental data on the Bechgaard salts, and the agreement is satisfactory.
Systematic studies of transport properties in deoxygenated Y(1-x)CaxBa2Cu3O6.1 series allowed to propose a diagram of conductivity mechanisms for this system. At intermediate temperature a variable range hopping (VRH) in 2 dimensions prevails. At lower temperature VRH in the presence of a Coulomb gap for smaller x and VRH in 2 dimensions for larger x are found. In a vicinity of superconductivity we observe conductivity proportional to \sqrt{T}. Thermally activated conductivity dominates at higher temperature. This diagram may be universal for the whole family of undoped high Tc related cuprate…
Magnetotransport theory of layered superconductors in the flux flow steady state is revisited. Longstanding controversies concerning observed Hall sign reversals are resolved. The conductivity separates into a Bardeen-Stephen vortex core contribution, and a Hall conductivity due to moving vortex charge. This charge, which is responsible for Hall anomaly, diverges logarithmically at weak magnetic field. Its values can be extracted from magetoresistivity data by extrapolation of vortex core Hall angle from the normal phase. Hall anomalies in YBCO, BSCCO, and NCCO data are consistent with theoret…
Several models of the electronic spectrum in the pseudogap state of underdoped cuprates have been proposed to explain ARPES and STM measurements, which reveal only truncated Fermi pockets instead of a full metallic Fermi surface. We consider the transport properties expected of four physically distinct models, and calculate the thermal and electrical conductivity of the electronic quasiparticles. By proposing transport currents that reflect the close correspondence between quasiparticles on the Fermi pockets in the pseudogap and those near nodes in the superconducting state, we show that measu…
