Pseudogap and fluctuation conductivity in Y1–xPrxBa2Cu3O7–δ single crystals with different praseodymium content
A.V. Solovjov, L.V. Omelchenko
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Nauky Ave., Kharkiv 61103, Ukraine
R.V. Vovk, and S.N. Kamchatnaya
Karazin Kharkov National University, 4, Svobody Sq., Kharkov 61077, Ukraine
Received Jule 12, 2016, revised February 21, 2017
In present work the effect of praseodymium doping on the excess conductivity σ'(T) and the pseudogap (PG) Δ*(T) in Y1–xPrxBa2Cu3O7–δ single crystals with Pr concentration change from х = 0 to х = 0.43 are investigated. It has been established that as the value of x increases, the resistance of the samples increases, and the critical temperature Tc decreases. In this case, the shape of the ρ(T) curves varies from the metallic (x ≤ 0.34) to the typical for underdoped YBa2Cu3O7–δ single crystals with a characteristic thermal activation deflection (x > 0.34). Regardless of the value of x, near Tc σ'(T) it is well described by the fluctuation theories of Aslamazov–Larkin and Maki–Thompson, demonstrating the 3D–2D crossover with increasing temperature. The crossover temperature T0 makes it possible to determine the coherence length along the c axis, ξc(0). At x = 0, Δ*(T) shows a maximum characteristic for YBCO films at Tpair ≈ 110 K. As x increases, the maximum at Tpair is blurred out, but a pronounced maximum Δ*(T) appears in the high-temperature region, fol-lowed by a linear section with positive slope. This dependence Δ*(T) is typical for magnetic superconductors and is most likely due to the influence of the intrinsic magnetic moment Pr (mPr ≈ 4μB).