Role of structural disorder in artificially layered high-temperature superconductors

Abstract

The electrical transport properties of (BaCuO 2 ) 2 /(CaCuO 2 ) 2 superconducting artificial structures, grown by pulsed laser deposition stacking in sequence nonsuperconducting individual BaCuO 2 and CaCuO 2 layers, have been studied. Such artificially layered materials have T c values up to 80 K and show a number of unusual properties such as the relatively high normal state resistivity with a nonlinear dependence on temperature, the enhanced thermodynamic fluctuations, the relatively low value of the critical temperature with respect to the natural compounds with the same number of CuO 2 planes, and the same carrier concentration. It is demonstrated that such properties can be explained if the high level of structural disorder, typical of these artificial structures, is considered.

Very Large Purely Intralayer Critical Current Density in Ultrathin Cuprate Artificial Structures

“…Thinner CR blocks (M 3) resulted in a decrease of T c possibly because of the occurrence of interface effects at the substrate/film and film/cap-layer interfaces. Furthermore, structures with N 1 were found to have a lower T c possibly because of the increased role of structural disorder in such thin IL blocks [26]. Therefore we decided to carry out J c measurements mostly on 5=2=5 structures and 2 2 superlattices.…”

Structural features of(Ba2Cu2O4Balestrino1, Pasquini2, Tebano3 2000Phys. Rev. BSelf Cite17080View full textAdd to dashboardCite

“…4 These superlattices, grown under appropriate temperature and oxygen pressure conditions, can have a superconducting transition temperature T c as high as 80 K. 12 All their superconducting properties are drastically affected by the large degree of structural disorder present. 13 Recently it has been shown by EXAFS and x-ray diffraction measurements in (Ba 2 Cu 2 O 4ϩx )/(CaCuO 2 ) n superlattices 14,15 that the crystallographic structure of the Ba block consists of a sequence of four atomic planes, namely CuO 2 /BaO/Cu 1Ϫ␦ O x /BaO with c 1 ϭ8.9 Å. The Ca block consists of a sequence of CuO 2 and Ca planes and has a true infinite layer ͑IL͒ structure with c 2 ϭ3.2 Å.…”

Superconducting properties of[BaCuOx]2/[CaCuOBalestrino1, Lavanga2, Medaglia3 et al. 2000Phys. Rev. BSelf Cite300180View full textAdd to dashboardCite

“…It decreases both for n larger than 3 and smaller than 2. Such an effect was explained on the basis of the structural disorder (especially effective for small n) and of the variation of the effective carriers concentration with n. Furthermore it was demonstrated that some peculiar features of the temperature dependence of the resistivity (its relatively high residual value, its pronounced rounding above T c and its saturation above room temperature) can be well explained by taking into account the role of the interfacial structural disorder that arises at the blocks interfaces [4]. Following this considerations, we believe that the role of the structural disorder is strongly reduced for the superlattices with thick IL blocks, negligible for the thickest ones.…”

“…In our previous work on the CBCCO − 2 × n system, we investigated both the dependence of the critical temperature on n (for n ranging from 1 to 6) and the influence of the interfacial structural disorder, typical for these artificial structures, on the electrical transport properties [4,5]. It was found that the critical temperature reaches the maximum value of about 80 K for n between 2 and 3.…”

“…been shown that the doping is nearly optimal (p ≃ 0.18 − 0.19 holes/CuO 2 plane) and T c ≃ 80 K [3,4].…”