Influence of strong electron irradiation on fluctuation conductivity and pseudogap in YBa2Cu3O7−δ single crystals

Abstract

The effect of high-energy electron irradiation on the temperature dependences of the resistivity ρ(), fluctuation conductivity (FLC), and pseudogap (PG) Δ*() of YBa2Cu3O7−δ (YBCO) single crystals containing virtually no twins was studied. A linear increase in the resistivity and a linear decrease in the superconducting (SC) transition temperature Tc with increasing irradiation doses φ were observed. For relatively small φ, the linear Tc can be described by the Abrikosov-Gorkov (AG) pair breaking theory, and for large φ, by the Emery-Kivelson (EK) theory, which takes into account the suppression of Tc by quantum phase fluctuations caused by irradiation defects. As FLC shows, at the average value of φ3=2.5×1019e/cm2, which corresponds to the AG-EK crossover, the distance between the conducting CuO2 planes, d01, as well as the coherence lengths along the c axis, ξc(0), and the region of SC fluctuations, ΔTfl, increase sharply, and the two-dimensional contribution of the Maki-Thompson fluctuations (2D-MT) unexpectedly changes to the two-dimensional contribution of the Aslamazov-Larkin (2D-AL). Surprisingly, no features in ρ(φ) and Tc(φ) indicating the AG-EK crossover are observed. At the same time, at φ3, a sharp increase in the opening temperature of PG, *, as well as the value of PG, Δ*, is observed, which indicates a possible decrease in DOS under the influence of defects. With a further increase in φ, all the parameters of PG and its dimensions are greatly reduced, and an unusual shape of Δ*() is found. However, quite unexpectedly, at φ5=5.6×1019e/cm2 the temperature dependences of both FLC and PG demonstrate curves typical for well-structured YBCO, regardless of the number of defects. Published by the American Physical Society 2025