Fluctuation-induced conductivity analyses of Be-doped (Bi0.25Cu0.25Li0.25Tl0.25)Ba2Ca2Cu3O10.δ superconductors in the critical regime and beyond

We have successfully synthesized (Bi0.25Cu0.25Li0.25Tl0.25)Ba2Ca2Cu3O10-delta,5 and (Bi0.25Cu0.25Li0.25Tl0.25)Ba-2(Ca1.5Be0.5)Cu3O10-delta samples and studied their excess conductivity analyses (fluctuation-induced conductivity) of resistivity data. The main objective of such analyses is to investigate the influence of Be-substitution on the superconductivity parameters at the microscopic level. The width of the 3D-2D Lawrence-Doniach regime is increased with the doping of Be at the Ca sites. The energy required to break apart the Cooper pairs is increased from 0.03 eV to 0.08 eV in Be-doped samples. Using the Ginzburg-Landau number (N-G) and GL equations, the thermodynamic critical magnetic field B-c(0), the lower critical field B-c1(0), the upper critical field B-c2(0), the critical current density J(c)(0), and penetration depth lambda(p.d) are also calculated from these analyses. The values of critical fields [B-c(0) B-c1(0)], J(c)(0), and phase relaxation time tau(phi) increased whereas the penetration depth lambda(p.d) and kappa values are suppressed with Be-doping. It is most likely that as a result of the enhancement in the density of the carriers in the (Bi0.25Cu0.25Li0.25Tl0.25)Ba2(Ca1.5Be0.5)Cu3O10-delta sample, this charge density gap is suppressed, which in turn suppresses the pseudo-gap resulting into enhancement of B-c (0), B-c1(0), and J(c) (0). (C) 2012 American Institute of Physics. [doi: 10.1063/1.3681325]