Effect of screening of the electron-phonon interaction on the temperature of Bose-Einstein condensation of intersite bipolarons

Here we consider an interacting electron-phonon system within the framework of extended Holstein-Hubbard model at strong enough electron-phonon interaction limit in which (bi)polarons are the essential quasiparticles of the system. It is assumed that the electron-phonon interaction is screened and its potential has Yukawa-type analytical form. An effect of screening of the electron-phonon interaction on the temperature of Bose-Einstein condensation of the intersite bipolarons is studied for the first time. It is revealed that the temperature of Bose-Einstein condensation of intersite bipolarons is higher in the system with the more screened electron-phonon interaction.Comment: 6 pages, 4 figure

Signatures of room-temperature superconductivity emerging in two-dimensional domains within the new Bi/Pb-based ceramic cuprate superconductors at ambient pressure

We predict the possibility of realizing room-temperature superconductivity in different 2D domains within the ceramic high-Tc cuprates at ambient pressure and experimentally confirm this prediction of 2D room-temperature superconductivity in the newly derived Bi/Pb-based ceramic cuprates containing many grain boundaries, interfaces and multiplate blocks. We argue that, in these high-Tc materials, besides bulk superconductivity in 3D domains there is also strongly enhanced 2D superconductivity emerging in the 3D-2D crossover region well above the superconducting transition temperature Tc. We study the possibility of the existence of distinct 3D and 2D superconducting phases in high-Tc ceramic cuprates, in which the unconventional Cooper pairs behave like bosons and condense below certain critical temperatures into 3D and 2D Bose superfluids in 3D and 2D domains. We show that the superconducting transition temperature in 2D domains is much higher than in 3D domains and can reach up to room temperature. We report signatures of room-temperature superconductivity occurring at different grain boundaries and 3D/2D interfaces and in multiplate blocks within the ceramic superconductors, synthesized by using the new melt technology in a large solar furnace. The samples of these materials synthesized under the influence of concentrated solar energy have the bulk Tc values ranging from 100 K to about 140 K and the more higher superconducting transition temperatures, possibly even as high as room temperature in the 3D-2D crossover region. The remnant 2D superconductivity in newly derived Bi/Pb-based ceramic cuprate superconductors is observed at temperatures 200-300 K well above the bulk Tc and the onset of room-temperature superconductivity is evidenced by the observations of a sharp step-like drop in the resistance and a well-detectable partial Meissner effect at around 300 K and ambient pressure