Diamagnetism above Tc in underdoped Bi2.2Sr1.8Ca2Cu3O10+d

TL;DR

This study investigates diamagnetism above Tc in highly underdoped Bi2223 crystals, revealing increased fluctuation diamagnetism with underdoping, which suggests changes in superconducting dimensionality and vortex liquid behavior.

Contribution

It provides new insights into the fluctuation diamagnetism in underdoped Bi2223, highlighting the relationship between doping level and superconducting fluctuations above Tc.

Findings

Diamagnetism above Tc increases with underdoping.

Underdoped samples show decreased superconducting dimensionality.

Enhanced vortex liquid fluctuations are observed in underdoped crystals.

Abstract

Single crystals of ${\rm Bi}_{2+x}{\rm Sr}_{2-x}{\rm Ca}_{2}{\rm Cu}_{3}{\rm O}_{10+\delta}$(Bi2223) with $x=0.2$ were grown by a traveling solvent floating zone method in order to investigate the superconducting properties of highly underdoped Bi2223.Grown crystals were characterized by X-ray diffraction, DC susceptibility and resistivity measurements, confirming Bi2223 to be the main phase.The crystals were annealed under various oxygen partial pressures to adjust their carrier densities from optimally doped to highly underdoped.The fluctuation diamagnetic component above the superconducting transition temperature $T_{\rm c}$ extracted from the anisotropic normal state susceptibilities $\chi_{ab}(T)$ ($H\perp c$) and $\chi_{c}(T)$ ($H\parallel c$) was found to increase with underdoping, suggesting a decrease in the superconducting dimensionality and/or increase in the fluctuating vortex liquid region.