Existence of superconductivity in oxygen-disordered YBa2Cu3O7−δ

Abstract

Understanding the role of CuO2 planes and Cu(1)-O(1) chains is critical to the mechanism for high-temperature superconductivity in YBa2Cu3O7−δ. By applying low-energy nanosecond excimer laser radiation on epitaxial single-crystal YBa2Cu3O7 thin films on various substrates, we have shown that superconductivity can exist in these specimens even when the Cu(1)-O(1) chains are disordered. Raman results show that ultrarapid controlled laser heating and cooling rates (∼109–1010 K/sec) result in selective disordering of the weakly bonded copper-oxygen chains without affecting the oxygen in the copper-oxygen planes. Microstructure-property correlations showed the existence of two regimes. In regime I, which exists below a certain laser-energy-density threshold, no degradation in the superconducting properties was observed even though the scattering efficiency of the Raman signal from the Cu(1)-O(4) vibrations is strongly diminished. The scattering efficiency of the Cu(1)-O(4) vibrations has been attributed to the Cu(1)-O(1) chains. Above the threshold laser fluence, regime II initiates, which is accompanied by concomitant degradation in the microstructure as well as in the superconducting properties. This regime has been correlated with the melting of near-surface regions in the film.

Source-reported materials — not catalogue approval

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