Electronic transport properties of intermediately coupled superconductors: PdTe2 and Cu0.04PdTe2

We have investigated the electrical resistivity, Seebeck coefficient and thermal conductivity of PdTe2 and 4% Cu intercalated PdTe2 compounds. Electrical resistivity for the compounds shows Bloch-Gruneisen type linear temperature (T) dependence for 100 K < T < 480 K, and Fermi liquid behavior (~ T^2) below 50 K. Seebeck coefficient data exhibit strong competition between Normal (N) and Umklapp (U) scattering processes at low T. Though our results indicate the transfer of charge carriers to PdTe2 upon Cu intercalation, it is difficult to discern any change in the Fermi surface of the compound by Nordheim-Gorter plots. The estimated Fermi energies of the compounds are quite comparable to good metals Cu, Ag and Au. The low T, thermal conductivity (k) of the compounds is strongly dominated by the electronic contribution, and exhibits a rare linear T dependence below 10 K. However, high T, k(T) shows usual 1/T dependence, dominated by U scattering process. The electron phonon coupling parameters, estimated from the low T, specific heat data and first principle electronic structure calculations suggest that PdTe2 and Cu0.04PdTe2 are intermediately coupled superconductors.Comment: 18 pages, 6 figure

Growth, Characterization, Vortex Pinning and Vortex Flow Properties of Single Crystals of Iron Chalcogenide Superconductor FeCr0.02_{0.02}Se

We report the growth and characterization of single crystals of iron chalcogenide superconductor FeCr$_{0.02}$Se. There is an enhancement of the superconducting transition temperature (T$_{\rm c}$) as compared to the T$_{\rm c}$ of the single crystals of the parent compound Fe$_{1+x}$Se by about 25%. The superconducting parameters such as the critical fields, coherence length, penetration depth and the Ginzburg-Landau parameter have been estimated for these single crystals. Analysis of the critical current data suggests a fluctuation in electronic mean free path induced ($\delta l$) pinning mechanism in this material. Thermally activated transport across the superconducting transition in the presence of external magnetic fields suggests a crossover from a single vortex pinning regime at low fields to a collective flux creep regime at higher magnetic fields. The nature of charge carriers in the normal state estimated from the Hall effect and thermal transport measurements could provide crucial information on the mechanism of superconductivity in Fe-based materials.Comment: 2 additional figures, additional discussion on nature of charge carrier