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We have fabricated submicron YBa2Cu3O7−x grain boundary junctions using [100] tilt bicrystal substrates. In these substrates, crystal planes are tilted around the b-axis, parallel to the bicrystal line. We have obtained high-quality junctions and fitted experimental data using a recently theory accounting for d-wave symmetry of the order parameter in layered superconductors with arbitrary orientation. In our experiment, sensitive to the amplitude of the pairing state, lobes of different signs do not influence the electrical transport in the junction. Nevertheless, the effects of a non-conventional symmetry are clearly observed on the temperature dependence of the critical current.

We have fabricated and analyzed submicron YBa2Cu3O7−x grain boundary Josephson junctions grown on [100] tilt SrTiO3 bicrystal substrates. We present an experiment sensitive to the amplitude of the order parameter. To this aim, we have measured electrical properties of [100] tilt bicrystal YBa2Cu3O7−x grain boundary junctions with nominal widths of 700 nm and 300 nm. Junctions are fabricated so that positive lobes of the d-wave electrodes face one another (d0–d0 junction). We demonstrate that, in such devices, the temperature dependences of the critical current may be accounted for by very high-transparency junction barriers, in which the influence of nodes in the pair potential is an essential element. We based our analysis on a recent theoretical model that, starting from the Bogoliubov–de Gennes equations, takes into account the presence of Andreev bound states in layered superconductors, with Cu–O planes tilted with respect the substrate plane, as is the case of [100] tilt grain boundary junctions.