Professor Paolo G. Radaelli OSI

Abstract:

We have extended the calcium solid-solubility limit in La2-xCaxCuO4 to x = 0.2 using synthesis at high oxygen pressure. The superconducting transition temperature increases with doping to 34 K at x = 0.15 and is suppressed for x > 0.15, similar to the Sr-substituted material. At a fixed doping level, the optimum superconducting properties (the highest Tc) are found for flat and square CuO2 planes. © 1994.

Abstract:

The first cuprate superconductor containing double (HgO)2 layers was synthesized using a high-pressure, high-temperature technique. The compound, with chemical formula Hg2Ba2Y1-xCaxCu2O 8-δ, contains a rock salt-type double HgO layer. The prototype compound Hg2Ba2YCu2O8-δ is an insulator. Superconductivity is induced in the system by partially replacing yttrium with calcium. © 1994.

Abstract:

We have studied the 1:2:4 phase of the YBaCuO compound by means of tunneling spectroscopy on single crystal based junctions. The crystals, with Tc≈80 K, have been chemically etched before the deposition of the counterelectrode in form of a thin film through a metallic mask. We have compared the tunneling spectra to those obtained on the Y123 system. The features at ±20 mV of the 1:2:3 phase are still observed in the 1:2:4 phase, while the low bias features at ±5 mV are not present in the tunneling characteristics of the Y124 compound. The experimental results are discussed in terms of the different CuO chain role in the Y123 and Y124 systems. © 1994.