Influence of annealing on the electrical resistance of YBCO single crystals

Abstract

The effect of annealing on the basal-plane electrical resistivity of the YBa2Cu3O 7−δ single crystals is studied in a broad range of oxygen contents. Within the framework of s-d scattering of electrons by phonons, an increase in the oxygen deficit index, δ, leads to a significant increase in the Debye temperature, θ, which is associated with the isotropization of the phonon spectrum as the concentration of oxygen vacancies increases. Near the optimal doping, the role of the paraconductivity becomes crucial, whereas its contribution decreases with increasing δ. At large values of δ some deviations from the s-d model of electron scattering by phonons are observed at room temperature, while no paraproductivity is observed. In the superconducting transition region, a 2D-3D crossover is observed, which shifts in the direction of Tc with increasing δ. The estimate for the transverse coherence length is about 1Å.

Распределение кислорода в структуре тонких пленок YBa-=SUB=-2-=/SUB=-Cu-=SUB=-3-=/SUB=-O-=SUB=-7-delta-=/SUB=- после хранения в вакууме при 300 K

“…1, таблица). В макроскопических монокристаллах YBCO наблюдали свидетельства существования сверхпроводящих областей с разными, но близкими T c , т. е. областей с разными значениями δ [26]. В таком случае исчезновение электрического сопротивления связали с образованием кластера областей с одинаковой T c , который распространялся на весь образец.…”

“…Нанофизика и наноэлектроника" 921 содержании кислорода в монокристаллах авторы [26] не предложили, но несомненно, что она зависит от вариации содержания кислорода, подобной наблюдаемой в кристаллитах пленок 2, 3, 4 после осаждения или хранения в вакууме (рис. 4).…”

Transverse conductivity and the pseudogap in YBCO single crystals irradiated with fast electrons

“…The YBa 2 Cu 3 O 7−δ single crystals were grown by the solution-melt technique as in Ref. 28. The electrical resistance was measured in the eight-point geometry illustrated in Ref.…”

“…[1][2][3][4][5], both the PG nature and its role in the formation of the superconducting state in HTSs remain unclear. In this regard, most promising are YBa 2 Cu 3 O 7−δ compounds 6,7 whose composition can be easily varied by substitution of Y for its isoelectronic analogues, 8,9 variation of the oxygen nonstoichiometry 10,11 or extreme exposures. [12][13][14][15] Until recently, it was believed 4,5 that, in the electronic transport properties, the PG manifests itself via a sublinear temperature dependence of the basal-plane electrical resistance.…”

Modification by high pressure of fluctuation paraconductivity of underdoped HoBa2Cu3O7-δ single crystals

“…The question about the influence of the dimensionality to the formation of the superconducting state of HTSC cuprates is still open [1][2][3][4][5]. In spite of 30 years of intense experimental and theoretical studies, the microscopic nature of high T c superconductivity is still unclear [6,7].…”