On Signatures of Room-Temperature Superconductivity Emerging in Bi/Pb Multiphase Cuprates Fabricated by the Solar Technology

Abstract

In this work, we experimentally investigate the possible coexistence of distinct 3D and 2D superconducting phases in high-T_c ceramic cuprates. In these materials, unconventional tightly bound polaronic Cooper pairs are expected to exhibit bosonic behavior and undergo condensation below characteristic critical temperatures, forming 3D and 2D Bose superfluid states within their respective regions. According to the theoretical model, the superconducting transition temperature associated with 2D regions can substantially exceed that of the bulk 3D phase and may, under suitable conditions, approach room temperature. Experimental signatures for possible room-temperature superconductivity is reported at grain boundaries, 3D/2D interfaces, and within multiplate structures of ceramic superconductors with the composition Bi_1.7Pb_0.3Sr₂Ca_n−1Cu_nO_y (where n = 2 − 30). These materials were synthesized using a novel melt-processing technique employing concentrated solar energy in a large solar furnace in Parkent. The resulting samples exhibit bulk T_c values ranging from approximately 100 to 140 K, together with significantly higher-temperature superconducting-like features associated with the 3D–2D crossover regime. Remnant 2D superconductivity-like features are observed at temperatures of approximately 200–300 K, substantially above the bulk T_c. Possible signatures of the onset of room-temperature superconductivity include a sharp, step-like decrease in electrical resistance, a measurable partial Meissner effect near 300 K, and differences observed through comparative torque and resonant radio-frequency (RF) magnetometry measurements of samples prepared using conventional solid-state reaction and solar-energy-based synthesis methods.