Instabilities of the normal state in current-biased narrow superconducting strips

We study the current-voltage characteristic of narrow superconducting strips in the gapless regime near the critical temperature in the framework of the Ginzburg-Landau model. Our focus is on its instabilities occurring at high current biases. The latter are consequences of dynamical states with periodic phase-slip events in space and time. We analyze their structure and derive the value of the reentrance current at the onset of the instability of the normal state. It is expressed in terms of the kinetic coefficient of the time-dependent Ginzburg-Landau equation and calculated numerically

Quantum Fluctuations and Dynamic Clustering of Fluctuating Cooper Pairs

We derive exact expressions for the fluctuation conductivity in two dimensional superconductors as a function of temperature and magnetic field in the whole fluctuation region above the upper critical field H_{c2}(T). Focusing on the vicinity of the quantum phase transition near zero temperature, we propose that as the magnetic field approaches the line near H_{c2}(0) from above, a peculiar dynamic state consisting of clusters of coherently rotating fluctuation Cooper-pairs forms and estimate the characteristic size and lifetime of such clusters. We find the zero temperature magnetic field dependence of the the transverse magnetoconductivity above H_{c2}(0) in layered superconductors.Comment: 5 pages, 3 figure

Electron Transport Properties of Composite Ferroelectrics

We study electron transport in composite ferroelectrics --- materials consisting of metallic grains embedded in a ferroelectric matrix. Due to its complex tunable morphology the thermodynamic properties of these materials can be essentially different from bulk or thin-film ferroelectrics. We calculate the conductivity of composite ferroelectrics by taking into account the interplay between charge localization, multiple grain boundaries, strong Coulomb repulsion, and ferroelectric order parameter. We show that the ferroelectricity plays a crucial role on the temperature behavior of the conductivity in the vicinity of the ferroelectric-paraelectric transition.Comment: 6 pages, 3 figure