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
E-mail: solovjov@ilt.kharkov.ua

R.V. Vovk, and M.A. Obolenskii

V. Karazin Kharkov National University, 4 Svobody Sq., Kharkov 61077, Ukraine
pos Анотація:

Received March 17, 2011

Abstract

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.

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