Crystal growth and in-plane optical properties of Tl2Ba2Can−1CunOx (n=1,2,3) superconductors

Abstract

Single crystals of thallium-based cuprates with the general formula Tl2Ba2Can−1CunOx (n=1,2,3) have been grown by the flux method. The superconducting transition temperatures determined by the ac magnetic susceptibility are 92, 109, and 119K for n=1,2,3, respectively. X-ray diffraction measurements and an EDX compositional analysis were described. We measured in-plane optical reflectance from room temperature down to 10K, placing an emphasis on Tl-2223. The reflectance roughly has a linear-frequency dependence above the superconducting transition temperature, but displays a pronounced knee structure together with a diplike feature at higher frequency below Tc. Correspondingly, the ratio of the reflectances below and above Tc displays a maximum and a minimum near those feature frequencies. In particular, those features in Tl2223 appear at a higher-energy scale than Tl2212 and Tl2201. The optical data are analyzed in terms of the spectral function. We discussed the physical consequences of the data in terms of both clean and dirty limits.

Source-reported materials — not catalogue approval

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