Search

We present a comparative study of our valence band photoemission results on Nb2Pd1.2Se5 and Nb2Pd0.95S5 superconductors which is supported by our DFT based electronic structure calculations. We observe that the VB spectra of both the compounds are qualitatively similar, except slight difference in the binding energy position of all features between the two compounds which could be the result of different electronegativity of Se and S atom. The calculated density of states reveal that the VB features are mainly composed of Pd Se S hybridized states. The nature of DOS originating from the distinctly coordinated Pd atoms is different. Further, the involvement of the various Pd 4d and Nb 4d states in crossing of Fermi level signifies the multiband character of these compounds. In addition, we find a temperature dependent pseudogap in Nb2Pd0.95S5 which is absent in Nb2Pd1.2Se5.

We present a comparative study of the valence band electronic structure of Pd based ternary chalcogenide superconductors Nb2Pd0.95S5, Ta2Pd0.97S6 and Ta2Pd0.97Te6 using experimental photoemission spectroscopy and density functional based theoretical calculations. We observe a qualitatively similarity between valence band (VB) spectra of Nb2Pd0.95S5 and Ta2Pd0.97S6. Further, we find a pseudogap feature in Nb2Pd0.95S5 at low temperature, unlike other two compounds. We have correlated the structural geometry with the differences in VB spectra of these compounds. The different atomic packing in these compounds could vary the strength of inter-orbital hybridization among various atoms which leads to difference in their electronic structure as clearly observed in our DOS calculations.

We report synthesis, structural details and electrical transport properties of topological insulator Bi2Te3. The single crystalline specimens of Bi2Te3 are obtained from high temperature (950C) melt and slow cooling (2C/hour). The resultant crystals were shiny, one piece (few cm) and of bright silver color. The Bi2Te3 crystal is found to be perfect with clear [00l] alignment. The powder XRD pattern being carried out on crushed crystals showed that Bi2Te3 crystallized in R3m symmetry with a = b = 4.3866(2) A, c = 30.4978(13) A and Gamma = 120degree. The Bi position is refined to (0, 0, 0.4038 (9)) at Wyckoff position 6c and of Te are (0, 0, 0) at Wyckoff position 3a and at (0, 0, 0.2039(8)) at 6c. Ambient pressure and low temperature (down to 2K) electrical transport measurements revealed metallic behavior. Magneto transport measurements under magnetic field showed huge non saturating magneto resistance (MR) reaching up to 250% at 2.5K and under 50KOe field. Summarily, the short communication clearly demonstrates that Bi2Te3 topological insulator exhibit non-saturating large positive MR at low temperature of say below 10K. The non saturating MR is seen right up to room temperature albeit with much decreased magnitude. Worth mentioning is the fact that these crystals are bulk in nature and hence the anomalous MR is clearly an intrinsic property and not due to the size effect as reported for nano-wires or thin films of the same., Comment: 11 pages text+Figs: Short Letter to editor MS: Comments/suggestions welcome: awanavps.webs.com

Superconducting order parameter and its symmetry are important parameters towards deciphering the pairing mechanism in newly discovered superconducting systems. We report a study on penetration depth measurement on Nb2PdS5 that has recently been reported with extremely high upper critical field with possible triplet pairing mechanism. Our data show that at low temperatures the change in penetration depth is best fitted with BCS s-wave model for single gap. The zero-temperature value of the superconducting energy gap is estimated to be {\Delta}0 = 1.05 meV. The superfluid density in the entire temperature range is well described by single gap for {\lambda} (0) = 220 nm.