Steplike electric conduction in a classical two-dimensional electron system through a narrow constriction in a microchannel

Using molecular dynamics simulation, we investigate transport properties of a classical two-dimensional electron system confined in a microchannel with a narrow constriction. As a function of the confinement strength of the constriction, the calculated conductance in the simulations exhibits steplike increases as reported in a recent experiment [D. G. Rees et al., Phys. Rev. Lett. 106, 026803 (2011)]. It is confirmed that the number of the steps corresponds to the number of stream lines of electrons through the constriction. We verify that density fluctuation plays a major role in smoothing the steps in the conductance.Comment: 11 pages, 9 figure

Superconductivity in Fullerides

Experimental studies of superconductivity properties of fullerides are briefly reviewed. Theoretical calculations of the electron-phonon coupling, in particular for the intramolecular phonons, are discussed extensively. The calculations are compared with coupling constants deduced from a number of different experimental techniques. It is discussed why the A_3 C_60 are not Mott-Hubbard insulators, in spite of the large Coulomb interaction. Estimates of the Coulomb pseudopotential $\mu^*$, describing the effect of the Coulomb repulsion on the superconductivity, as well as possible electronic mechanisms for the superconductivity are reviewed. The calculation of various properties within the Migdal-Eliashberg theory and attempts to go beyond this theory are described.Comment: 33 pages, latex2e, revtex using rmp style, 15 figures, submitted to Review of Modern Physics, more information at http://radix2.mpi-stuttgart.mpg.de/fullerene/fullerene.htm

Superconducting properties of fullerenes in the mixed state (Review Article)

A review of magnetization measurements and their evaluation in terms of critical fields and characteristic lengths in fullerene superconductors is presented. Typical results of magnetization curves are shown and the evaluation of the superconducting fraction from these measurements is discussed. We also discuss results on determination of the critical fields and characteristic lengths by different experimental techniques and make a comparison of these results between granular and crystalline samples

Preparation and characterization of Rb3C60 bulk single crystals

Rb3C60 crystals with a size of several tenths of a millimetre were prepared by doping C60 crystals in rubidium vapour. Experiments with different annealing times and various annealing temperatures and temperature gradients were performed to assess the optimal conditions for homogeneous doping. The crystals were characterized by ac magnetization measurements. Doping at 463 K with 10% excess of rubidium and annealing at 685 K for 27 days were found to produce the best crystals with almost 100% of the superconducting Rb3C60 phase

Nonlinear surface electron transport over liquid helium

We present experimental data and a theoretical analysis of nonequilibrium mobility of surface electrons in liquid helium. The experiments are carried out in the temperature range where electron mobility is limited by electron scattering at surface excitations of liquid helium (ripplons). Holding and driving electric fields of wide ranges are used in measurements. Special attention is paid to the condition of strong holding fields under which hot electrons are confined to the ground surface level. Depending on the relation between the momentum relaxation rate and electron–electron collision frequency, different theoretical approaches are used to describe the nonlinear mobility of surface electrons. The results obtained allow to estimate the range of physical parameters where experimental data can be described by the theory of nonlinear electron transport within the ground surface level