Growth and post-annealing studies ofBi2Sr2−xLaxCuO6+δ (0≤x≤1.00) single crystals

Abstract

Bi2Sr2−xLaxCuO6+δ (0≤x≤1.00) single crystals with high quality have been grown successfully using thetraveling-solvent floating-zone technique. The patterns of x-ray diffraction suggesthigh crystalline quality of the samples. After post-annealing in flowing oxygen at600 °C, thecrystals show sharp superconducting transitions revealed by AC susceptibility. The hole concentrationp is deduced from the superconducting transition temperature(Tc), which exhibits a linear relation with La doping levelx. It ranges from the heavily overdoped regime(p≈0.2) to the extremelyunderdoped side (p≈0.08) where the superconductivity is absent. Comparing with the superconducting dome in theBi2+xSr2−xCuO6+δ system, the effects from out-of-plane disorders show up in our samples. Besides the La doping levelx, the superconductivity is also sensitive to the content of oxygen which could be tuned bythe post-annealing method over the whole doping range. The post-annealing effects onTc and p for each La doping level are studied and give some insights on the differences in naturebetween the overdoped and underdoped regimes.