Lattice softening in superconducting compositions of Ba(K)BiO3.

Influence of thermal fluctuations on the Nernst signal in superconducting (K,Ba)BiO3 single crystals

Direct transition from Bose glass to normal state in the (K,Ba)BiO3 superconductor.

The introduction of columnar defects in (K,Ba )Bi O3 single crystals shifts both the irreversibility and thermodynamic transition lines, respectively, deduced from ac susceptibility (and/or transport) and specific heat measurements, upwards. This shift can be attributed to the defect-induced decrease of the difference (Delta F) between the free energies in the superconducting and the normal sta...

Onset of dielectric modes at 110 K and 60 K due to local lattice distortions in nonsuperconducting YBa

We report the observation of two dielectric transitions at 110 and 60 K in the microwave response of nonsuperconducting YBa2Cu3O6.0 crystals. The transitions are characterized by a change in polarizability and presence of loss peaks, associated with overdamped dielectric modes. An explanation is presented in terms of changes in polarizability of the apical O atoms in the Ba–O layer, affected by...

Experimental aspects of Alpha, Beta angles distortion on superconductivity in 1111-type Iron-based superconductor

In this research, we aim to clarify the relationship between the structural distortion due to doping and the superconductivity existence in the FeAs4 structure. For this, we have prepared polycrystalline of NdFeAsO0.8F0.2, NdFeAs0.95Sb0.05O0.8F0.2 and Nd0.99Ca0.01FeAsO0.8F0.2 samples by one-step solid state reaction method. The structural and electrical properties of the samples were characteri...

Structural instability and superconductivity in Ba1−xKxBiO3

We report results of the ultrasonic investigation of Ba1−xKxBiO3 superconducting (SC) single crystals for two potassium concentrations x ∼= 0.35 and x ∼= 0.47 in a wide temperature range including the normal and the SC states. An instability of the crystal lattice that develops above the superconducting phase transition leads to a softening of both the transverse c44 and the longitudinal c11 mo...