Correlation between Tc and ns/m* in Bi2Sr2CaCu2O8+δ single crystals

Abstract The reversible magnetization measurements with applied field parallel to the c -axis were carried out for a series of Bi 2 Sr 2 CaCu 2 O 8+ δ (Bi2212) single crystals with different oxygen content varying from underdoped to overdoped states, from which the doping dependence of penetration depth and n s / m * can be obtained. It was firstly found in this system that with increasing oxygen content, the value of n s / m * increases in the underdoped region and reaches a maximum at the optimal doping, then decreases in the overdoped region. The observed deviation from the linear relationship of T c ∝ n s / m * in the underdoped region can be regarded to be due to the structural distortion and the disorder scattering, while the decrease of n s / m * in the overdoped region is suggested to be due to the phase-separation related pair breaking.