In superconductors the zero-resistance current-flow is protected from dissipation at finite temperatures (T) by virtue of the short-circuit condition maintained by the electrons that remain in the condensed state. The recently suggested finite-T insulator and the “superinsulating” phase are different because any residual mechanism of conduction will eventually become dominant as the finite-T insulator sets-in. If the residual conduction is small it may be possible to observe the transition to these intriguing states. We show that the conductivity of the high magnetic-field insulator terminating superconductivity in amorphous indium-oxide exhibits an abrupt drop, and seem to approach a zero conductance at T < 0.04 K. We discuss our results in the light of theories that lead to a finite-T insulator.

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Graphene-Polyvinyl alcohol (PVA) nanocomposite films with thickness 120µm were synthesized by solidification of PVA in a solution with dispersed graphene nanosheets. Electrical conductivity data were explained as arising due to hopping of carriers between localized states formed at the graphene-PVA interface. Dielectric permittivity data as a function of frequency indicated the occurrence of Debye-type relaxation mechanism. The nanocomposites showed a magnetodielectric effect with the dielectric constant changing by 1.8% as the magnetic field was increased to 1 Tesla. The effect was explained as arising due to Maxwell-Wagner polarization as applied to an inhomogeneous two-dimensional,two-component composite model. This type of nanocomposite may be suitable for applications involving nanogenerators.

Variations of the coherent resonance, i.e. an electromagnetically induced transparency (EIT) peak with the cell temperature in -and V-type systems are observed for the 85 Rb-D 2 transition. In a -type system, the amplitude of the EIT peak gradually decreases and it is finally masked by the broadened optical pumping dips with the increase of the cell temperature. But for the V-type system, the EIT and the saturation peaks are greatly enhanced with the increase of the cell temperature. The effect of the external magnetic field on the EIT resonance is also investigated considering both types of systems. For the -type system in place of a single EIT resonance, five transparency windows with broadened width and reduced contrast are obtained depending on the Zeeman levels formed by the applied magnetic field. In the V-type system, the coherent resonance peak could not be resolved in the presence of the external magnetic field, but a greater number of saturation peaks with broadened width appear in the probe transmission spectrum. A theoretical model is adopted to represent the experimental results. Good agreement is found between the experimental and numerically simulated results.

We report measurements of the in-plane London penetration depth λ in single crystals of the α-PdBi2 superconductor -the α-phase counterpart of the putative topological superconductor β-PdBi2, down to 0.35 K using a high-resolution tunnel-diode-based technique. Both λ and superfluid density ρs exhibit an exponential behavior for T ≤ 0.35Tc, with ∆(0)/kBTc ∼2.0, ∆C/γTc∼2.0 and λ(0)∼140 nm, showing that α-PdBi2 is a moderately-coupling, fully-gapped superconductor. The values of ∆(0) and ∆C/γTc are consistent with each other via strong-coupling corrections.

The Total Electron Content (TEC) measured from a station situated near the northern crest of the equatorial anomaly is compared with that obtained from models such as the Parameterized Ionospheric Model (PIM 1.6) and International Reference Ionosphere (IRI-95) for well over one solar cycle (1977 -1990). The limitations of conversion from vertical to slant TEC and vice versa as required for GPS ionospheric corrections in the equatorial region are discussed. It is found that the correspondence among the vertical TEC at the ionospheric pierce point, geometrically (sec ) converted slant TEC, and slant TEC along a GPS signal propagation path becomes poor for elevation angles of less than 80 deg. Based on this finding, an optimum grid size for reliable operation of the Satellite-Based Augmentation System (SBAS) in the Indian subcontinent (GAGAN, or GPS and GeoAugmented Navigation) is estimated. The suggested grid size is much smaller than the standard 5 ϫ 5 deg.