Pseudogap in CdBa2Cu3O7−δ HTSC material

Abstract

Long-lived minima are detected at Tmin1 = 275 K and Tmin2 = 252 K in the ρ(T) curve of polycrystalline CdBa2Cu3O7−δ, which has a superconducting transition at 86.8 K. It is shown that the excess conductivity Δσ(T) near Tmin obeys the classical Aslamazov-Larkin fluctuation theory. This suggests that fluctuation Cooper pairs may develop in CdBa2Cu3O7−δ at T ≫ Tc. The experimental data are used to calculate the coherence length ξc(0), the 2D-3D crossover temperature T0, and the interplanar pairing constants. The magnitude and temperature dependence of the pseudogap for a sample without the minima are found to be typical of cuprate HTSC materials.

Analysis of fluctuation conductivity in Y-=SUB=-0.5-=/SUB=-Cd-=SUB=-0.5-=/SUB=-Ba-=SUB=-2-=/SUB=-Cu-=SUB=-3-=/SUB=-O-=SUB=-7-delta-=/SUB=-

“…From this point of view, the compound YBa 2 Cu 3 O 7−δ (YBCO) is attractive due to the opportunity of wide variation of the composition by replacing yttrium with its isoelectronic analogs, or by changing the degree of oxygen nonstoichiometry. Note that yttrium in the composition of YBCO is easily replaced by most lanthanides and other elements [1,[21][22][23][24][25][26][27][28][29][30], which usually does not lead to deterioration of the SP properties of the initial composition. The exception is praseodymium, t. k. PrBCOdielectric [31,32].…”