Polyconductivity in polypyrrole: The correlated electron gas

p-toluensulfonate doped polypyrrole (PPy), undergoes an electric-field induced reversible transition from an insulating state to a highly conductive one. The spatially average field can be as small as 200 V/cm, when the temperature of the sample is below 20 K. The applied electric field leads to a sharp jump in the value of the current to a value which is nearly five orders of magnitude higher than before. When the applied electric field is reduced to below a critical value, the system switches back to a low conductive state. The effect is reversible, symmetric in voltage, and reproducible for different samples. The switching is, we believe, an electronic glass melting transition and it is due to the disordered, highly charged granular nature of PPy

Graphene nanotransistors for RF charge detection

We have studied the static and dynamical properties of a graphene microwave nanotransistor to be used as sensitive fast charge detectors. The channel consists of exfoliated graphene on SiO2 with a 120 nm long, 900-1500 nm wide top-gate deposited on 5 nm AlOx dielectric. The scattering parameters were measured up to 60 GHz from which we deduce the gate capacitance, the drain conductance and the transconductance as a function of gate voltage. The broad measuring band allows us to measure the current gain and to map its full spectrum so as to extract reliable values of the transit frequency fT. From these measurements, we could estimate the carrier mobility, the doping of the access leads, the gate capacitance and the transconductance. The transconductance per unit width and bias voltage is larger than 1mSμm−1 V−1 which compares with the performance of high electron mobility transistors. High-frequency characterization is achieved using microwave probe stations. Finally, using recent noise thermometry measurements, we estimate the charge resolution of graphene nanotransistors

Plan for nuclear symmetry energy experiments using the LAMPS system at the RIB facility RAON in Korea

A new rare isotope beam accelerator RAON and user facilities will be built in Korea. The Korea broad acceptance recoil spectrometer and apparatus (KOBRA) and the large-acceptance multipurpose spectrometer (LAMPS) will be ready from the beginning of the accelerator operation, and will be used to perform the nuclear physics experiments. We plan to use both spectrometers to investigate the density dependence of the nuclear symmetry energy in a wide range of beam energies. In particular, the high-energy setup of LAMPS, which is a combination of a solenoid and dipole spectrometers with neutron detector array, will be primarily used to study the symmetry energy of dense nuclear matter. This paper provides an overview of the RAON and the user facilities for the nuclear physics program with an emphasis on LAMPS

Towards an emerging understanding of non-locality phenomena and non-local transport

International audienceIn this paper, recent progress on experimental analysis and theoretical models for non-local transport (non-Fickian fluxes in real space) is reviewed. The non-locality in the heat and momentum transport observed in the plasma, the departures from linear flux-gradient proportionality, and externally triggered non-local transport phenomena are described in both L-mode and improved-mode plasmas. Ongoing evaluation of 'fast front' and 'intrinsically non-local' models, and their success in comparisons with experimental data, are discusse