owards a new kind of component: Superconductor Single Electron Transistor SSET

Single-electron transistors (SETs) are used to perform sensitive charge measurements and are widely discussed as possible components of dense integrated circuit. An exact model for a single-electron transistor (SET) was developed [1] early, within the circuit simulation package SPICE; it's constituted by two tunnel junctions, with two gates coupled to the island. We will present here a description of previews results of SET [1] and our perspective for a superconductor single electron transistor. Superconducting single-electron transistors (SSET's) are small islands of superconducting material isolated from an external circuit by tunnel barriers (Josephson junctions). The normal tunnel barrier resistances: R >RQ= h / 4e2 ≈ 6.5 KΩ are sufficient to constrain the excess charge on the island to integer multiples of e.Single-electron transistors (SETs) are used to perform sensitive charge measurements and are widely discussed as possible components of dense integrated circuit. An exact model for a single-electron transistor (SET) was developed [1] early, within the circuit simulation package SPICE; it's constituted by two tunnel junctions, with two gates coupled to the island. We will present here a description of previews results of SET [1] and our perspective for a superconductor single electron transistor. Superconducting single-electron transistors (SSET's) are small islands of superconducting material isolated from an external circuit by tunnel barriers (Josephson junctions). The normal tunnel barrier resistances: R >RQ= h / 4e2 ≈ 6.5 KΩ are sufficient to constrain the excess charge on the island to integer multiples of e

The vortex motion and the magnetization study in YBa2Cu3O7-d single crystal

We have investigated the vortex motion and the magnetization of high critical temperature superconductors YBa2Cu3O7-d Measurements were made using a vibrating sample magnetometer technique. Several magnetization hysteresis cycles have been obtained for different angles, θ, between the applied magnetic field, H, and the crystallographic c-axis. For T = 30 K we observed a central peak and for T = 80 K we observed a second peak or "fishtail".We have investigated the vortex motion and the magnetization of high critical temperature superconductors YBa2Cu3O7-d Measurements were made using a vibrating sample magnetometer technique. Several magnetization hysteresis cycles have been obtained for different angles, θ, between the applied magnetic field, H, and the crystallographic c-axis. For T = 30 K we observed a central peak and for T = 80 K we observed a second peak or "fishtail"

The critical current density and the vortex pinning in high quality YBa2Cu3O7-d thin films

We have measured the critical current density Jc of high quality c-axis oriented YBa2Cu3O7-d thin films. Measurements were performed for various magnetic field and temperature values, and as a function of the angle q between the c-axis and the applied magnetic field direction. A maximum of the critical current density was obtained when the flux lines are aligned along the CuO planes (q = 90°); another maximum in Jc was also observed when the magnetic field is adjusted parallel to the c-axis. We attribute these effects to different, intrinsic and extrinsic, pinning mechanisms of vortices in the sample.We have measured the critical current density Jc of high quality c-axis oriented YBa2Cu3O7-d thin films. Measurements were performed for various magnetic field and temperature values, and as a function of the angle q between the c-axis and the applied magnetic field direction. A maximum of the critical current density was obtained when the flux lines are aligned along the CuO planes (q = 90°); another maximum in Jc was also observed when the magnetic field is adjusted parallel to the c-axis. We attribute these effects to different, intrinsic and extrinsic, pinning mechanisms of vortices in the sample

High temperature superconductivity in SmBa2Cu3O 7-x : transport properties and effect of pressure

Sintered powders of SmBa2Cu3O7-x have been prepared and characterized. The physical properties, superconducting temperature transition, up to 92 K, magnetic susceptibility, electrical resistivity and thermopower have been studied as a function of the preparation conditions and therefore of oxygen stoichiometry. The upper critical field has been estimated from resistivity measurements in fields up to 8 T and the slope (dBc2/dT)Tc found to be close to 4 TK-1 for the highest Tc samples. Studies of the electrical resistivity under hydrostatic pressures up to 18 kbar show an increase of Tc under pressure with dTc/dp ∼ 0.5 K kbar-1. Finally measurements of voltage-current characteristics indicate that either Josephson junctions or superconductor-insulator-normal metal junctions can be found inside the samples, as expected in inhomogeneous materials.Les propriétés physiques, température de transition supraconductrice, susceptibilité magnétique, résistivité électrique et pouvoir thermoélectrique de poudres frittées de SmBa2Cu3O7-x, ont été étudiées en fonction des conditions de préparation et donc de la stoéchiométrie en oxygène. Le champ critique Bc2 a été estimé à partir de mesures de résistivité en champ maximum de 8 T et la pente (dBc2/dT) Tc a été trouvée voisine de 4 T K-1 dans les échantillons à plus haut Tc. Une étude de la résistivité sous pression hydrostatique (0-18 kbar) montre que Tc augmente avec la pression (dTc/dp = 0,5 K kbar-1). Enfin des mesures de caractéristique courant-tension indiquent que des jonctions de type Josephson ou de type S-I-N (Supraconducteur-isolant-métal normal) existent à l'intérieur des échantillons, par suite de l'inhomogénéité de composition

Angular studies of the magnetoresistance in the density wave state of the quasi-two-dimensional purple bronze KMo 6O 17

The purple molybdenum bronze KMo 6O 17 is a quasi-two-dimensional compound which shows a Peierls transition towards a commensurate metallic charge density wave (CDW) state. High magnetic field measurements have revealed several transitions at low temperature and have provided an unusual phase diagram “temperature-magnetic field”. Angular studies of the interlayer magnetoresistance are now reported. The results suggest that the orbital coupling of the magnetic field to the CDW is the most likely mechanism for the field induced transitions. The angular dependence of the magnetoresistance is discussed on the basis of a warped quasi-cylindrical Fermi surface and provides information on the geometry of the Fermi surface in the low temperature density wave state. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 200771.45.Lr Charge-density-wave systems, 72.15.Gd Galvanomagnetic and other magnetotransport effects,