Enhanced three-dimensional excess conductivity in Be-doped Cu0.5Tl0.5Ba2Ca3-xBex Cu4O12-δ (x=0,0.5,0.75,1.0,1.25,1.5) superconductors

We report the enhanced fluctuation-induced conductivity of Be-doped Cu0.5Tl0.5Ba2Ca3-xBex Cu4O12-delta (x=0,0.5,0.75,1.0,1.25,1.5) samples. The analysis has been done with partial substitution of Be in place of Ca. In each case excess conductivity has been analyzed and we tried to make a fit with the Aslamasov-Larkin (AL) and Lawrence-Doniach equations. It is observed that our data fit well with the three-dimensional (3D) AL equation, and a crossover from two dimensions to three dimensions has been found in our samples. We have also employed this transition to estimate the Josephson coupling strength in our samples. This interlayer coupling strength J, which controls the superconducting transition, has been found to improve with increased Be content. The Ginzburg-Landau coherence lengths xi(c)(0) for all cases have also been calculated. The Fourier transform infrared spectroscopy (FTIR) absorption measurements also provide a clue for the enhanced 3D fluctuations. The higher electronegativity, as well as smaller ionic size, of Be compared to Ca is suggested to be the possible source of promoting enhanced 3D character in Be-doped samples.