Preparation and picosecond optical response of Bi system high-Tc superconductors

Abstract Bi 2 Sr 2 Ca 1− x Y x Cu 2 O 8+ δ single crystals were grown by traveling solvent floating zone method. The crystallinity and the superconducting property of the single crystals were characterized by X-ray diffraction and in-plane resistivity measurements. To investigate the ultrafast optical response, time-resolved pump–probe reflectivity measurements were carried out on the single crystals. As a result, fairly long relaxation times of about 20 and 6 ps of excited carriers were estimated for the crystals with x =0 and 0.2, respectively, as compared to 1.7 ps for YBa 2 Cu 3 O 7− δ thin films in previous study. The relaxation time observed on the underdoped crystal with x =0.2 showed a good consistency with that of Bi 2 Sr 2 CaCu 2 O 8+ δ thin film in underdoped regime.