Low Temperature Physics: 37, 840 (2011); https://doi.org/10.1063/1.3670027 (3 pages)
Fizika Nizkikh Temperatur: Volume 37, Number 9-10 (September 2011), p. 1053-1056 ( to contents , go back )
Peculiarities of fluctuation conductivity and pseudogap behavior in slightly doped HoBa2Cu3O7-δ single-crystals under pressure
A.L. Solovjov, M.A. Tkachenko
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Lenin Ave., Kharkov 61103, Ukraine
R.V. Vovk, and M.A. Obolenskii
V. Karazin Kharkov National University, 4 Svobody Sq., Kharkov 61077, Ukraine
Received March 17, 2011
The effect of hydrostatic pressure up to 5 kbar on fluctuation conductivity σ′(T ) and pseudogap Δ*(T) of slightly doped high-Tc single crystals of HoBa2Cu3O7-δ is studied. It is shown that σ′(T ) near Tc is well described by Aslamazov–Larkin and Hikami–Larkin fluctuation theories demonstrating a 3D–2D crossover with increasing temperature. Δ*(T) exhibits two unexpected maxima at Tm1 ≈ 195 K and Tm2 ≈ 210 K possibly due to the two-phase state of the single crystal. The pressure-induced redistribution of labile oxygen leads to the disappearance of these peaks and a linear dependence Δ*(T) with a positive slope at high temperatures. It is essential that when the pressure is removed, these peaks are restored. In general, the dependences σ′(T ) and Δ*(T ) are markedly different from those that were obtained for YBCO films with different oxygen content. They resemble similar curves obtained for FeAs-based superconductor SmFeAsO0.85. The result can be explained by the influence of paramagnetism in HoBa2Cu3O7–δ.
PACS: 74.72.–h Cuprate superconductors.
Key words: high pressure, high-temperature superconductors, single crystals HoBa2Cu3O7-δ, fluctuation conductivity, coherence length, preudogap.