Resistive investigation of pseudogap state in non-stoichiometric ReBa 2Cu 3O 7− δ (Re = Y, Ho) single crystals with account for BCS–BEC crossover

Abstract

We investigate the conductivity in the basis plane of the non-stoichiometric ReBa 2Cu 3O 7− δ (Re = Y, Ho) single crystals. The excess conductivity (Δ σ) is described by Δ σ ∼ ( 1 − T / T * ) exp ( Δ a b * / T ) in the wide temperature range T f < T < T*, where T* is the mean field temperature of the superconducting transition. We determined that the temperature dependence of the pseudogap (PG) is described in terms of the BCS–BEC crossover theoretical model. It is observed that a reduction in the oxygen content leads to the widening of the temperature interval, in which the PG region is realized, and to the narrowing of the area of the ρ( T) linear dependence in the ab-plane.