Vortex Phase Dynamics in Yttrium Superhydride YH at Megabar Pressures.

A comprehensive study of vortex phases and vortex dynamics is presented for a recently discovered high-temperature superconductor YH with (onset) of 215 K under a pressure of 200 GPa. The thermal activation energy () is derived within the framework of the thermally activated flux flow (TAFF) theory. The activation energy yields a power law dependence ∝ on magnetic field with a possible crossover at a field around 8-10 T.

Phase Formation of Iron-Based Superconductors during Mechanical Alloying.

We successfully synthesized bulk BaNaFeAs and SrNaFeAs compounds by high-energy mechanical alloying (MA) technique. The MA process results in homogeneous amorphous phases of BaFeAs and SrFeAs. It was found that the optimum time for high-energy milling in all cases is about 1.

Synthesis and HRTEM Investigation of EuRbFeAs Superconductor.

In the stoichiometric iron-based superconductor EuRbFeAs, superconductivity coexists with a long-range magnetic ordering in Eu layers. Using high-resolution transmission electron microscopy (HRTEM), we observed an atomic structure of as-grown EuRbFeAs crystals. HRTEM shows that crystals have two-dimensional intrinsic nanoinclusions established to be the RbFeAs (122) phase with a volume fraction of ~5.

Electronic Structures and Surface Reconstructions in Magnetic Superconductor RbEuFeAs.

In pnictide RbEuFeAs, superconductivity sets in at 36 K and coexists, below 15-19 K, with the long-range magnetic ordering of Eu 4f spins. Here we report scanning tunneling experiments performed on cold-cleaved single crystals of the compound. The data revealed the coexistence of large Rb-terminated and small Eu-terminated terraces, both manifesting 1 × 2 and reconstructions.