Fluctuation induced conductivity and pseudogap state studies of Bi1.6Pb0.4Sr2Ca2Cu3O10+\u03b4 superconductor added with ZnO nanoparticles

Ali Aftabi,Morteza Mozaffari

doi:10.1038/s41598-021-83218-9

Abstract

The major limitations of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconductor are weak flux pinning capability and weak inter-grains coupling that lead to a low critical current density and low critical magnetic field which impedes the suppleness of this material towards practical applications. The addition of nanoscales impurities can create artificial pining centers that may improve flux pinning capability and intergranular coupling. In this work, the influences of ZnO nanoparticles on the superconducting parameters and pseudogap properties of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconductor are investigated using fluctuation induced conductivity analyses. Results demonstrate that the ZnO nanoparticles addition improves the formation of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ phase significantly. Various superconducting parameters include coherence length along c-axis (ξc(0)), penetration depth (λpd(0)), Fermi velocity (vF), Fermi energy (EF), lower and upper critical magnetic fields (Bc1(0) and Bc2(0) respectively) and critical current density (Jc(0)), are estimated for samples with different amounts of ZnO nanoparticles. It is found that the values of the Bc1(0), Bc2(0), and Jc(0) are improved significantly in the 0.2 wt% ZnO added sample in comparison to the ZnO-free sample. The magnitude and temperature dependence of the pseudogap Δ*(T) is calculated using the local pairs model. The obtained values of Tpair, the temperature at which local pairs are transformed from strongly coupled bosons into the fluctuating Cooper pairs, increases as the added ZnO nanoparticles concentration enhances up to 0.2 wt%. Also, the estimated values for the superconducting gap at T = 0 K (Δ(0)) are decreased from about 26 meV in ZnO-free sample to about 22 meV in 0.2 wt% ZnO added sample and then increases for higher values of additive.

Highlights

The superconducting pairing mechanism in high-temperature superconductor (HTS) materials remains rather controversial, more than three decades after their discovery[1,2]
The bonding energy of the fluctuating Cooper-pairs is inversely proportional to the coherence length, εb ~ 1/(ξab)[2], it noticeably increases with temperature enhancement
The X-ray diffraction (XRD) results indicated that the small amount of the ZnO NPs improves the formation of (Bi, Pb)-2223 phase significantly, which can be attributed to the grain connectivity improvement by ZnO N Ps15

Summary

Introduction

The superconducting pairing mechanism in high-temperature superconductor (HTS) materials remains rather controversial, more than three decades after their discovery[1,2]. This deviation is followed by a considerable rounding that is observed above the transition temperature Tc6,7 This deviation from linear behavior indicates thermal fluctuations of Cooper-pairs. FIC provides an opportunity to investigate the superconducting Cooper-pairs fluctuations behavior in a broad range of temperatures above T c. The study of the FIC has attracted significant attention in the research of the HTS materials[10,11,12,13,14] These interesting studies are keys to providing information about microscopic and superconducting parameters of the HTS materials such as Fermi velocity and Fermi energy of charge carriers, coherence length, cross over temperatures, phase relaxation time (lifetime) of fluctuating pairs, critical magnetic fields, and critical current density[6,8,15]. The effects of the ZnO NPs on the magnitude and temperature dependence of the pseudogap in (Bi, Pb)-2223 phase were studied

Methods

Results

Conclusion