Fiske steps and hysteresis in YBa2Cu3O7 grain boundary Josephson junctions: Structural information of the barrier by means of a nondestructive approach

Abstract

A deep analysis of the current-voltage ͑I-V͒ characteristics of YBa 2 Cu 3 O 7 grain boundary Josephson junctions ͑GBJJs͒ allows us to go much farther than the usual calculus of the transport parameters. It is possible to construct a structural image of the barrier by an exhaustive and complementary analysis of both transport and electromagnetic parameters obtained from I-V curves. For such an approach, we have chosen the following three representative bicrystalline geometries: 24°͓001͔ asymmetric, 45°͓100͔ asymmetric, and 24°͓001͔ symmetric +45°͓100͔ asymmetric. The dependence of the product I C R N on the junction normal resistance is of the I C R N −1 type pointing to a SNINS model ͑S denotes superconductor, I denotes insulator, and N denotes normal metal͒ for all our GBJJs. A satisfactory explanation of the discrepancy of the capacitance of the barrier estimated from Fiske resonance positions and hysteresis in the I-V curves needs of such a model. Moreover an estimation of the length of the normal regions adjacent to the crystallographic barrier can be made. This comparative analysis is presented in order to extract interesting information about the particular transport mechanisms involved in these GBJJs.

Amplitude sensitive experiment of pairing symmetry ind0–d0submicron Y–Ba–Cu–O bicrystal grain boundary junctions

“…Along the quasiparticle branch it is possible to observe current bumps or current steps, indicating the presence of resonances. We will not present data on such resonances in this paper, because we have already analyzed electromagnetic properties of micrometric [100] tilt YBCO grain boundary junctions elsewhere [29][30][31]. Moreover, resonances observed in submicron junctions and DC-SQUIDs made on the same chip will be presented in a separate paper [32].…”

Applications of High-Tc Superconductivity

“…The critical current density J c of symmetric 24 degree bicrystal Josephson junctions increases nearly linearly with the temperature dependence J c (T) ≈ ). The grain boundary of the YBCO bicrystal junctions behaves as if it were mostly dielectric with an average barrier thickness t ≈ 2 nm (Winkler et al, 1994) and dielectric constant ε ≈ 28 for the grain boundary region in YBCO (Navacerrada, 2008). Both the noise parameter Γ and the Stewart-McCumber parameter C β contribute to the voltage noise of the Josephson junctions (Voss, 1981) and, consequently, to the magnetic field resolution of the DC SQUID magnetometers.…”

Epitaxial Oxide Heterostructures for Ultimate High-Tc Quantum Interferometers

“…On the other hand, compared to the bicrystal junctions, production of SQUIDs with ramp junctions is more complicated and for a similar critical current I c their normal state resistance, R N , is about 3 times smaller leading to smaller voltage swings of the DC SQUID. The easier production of junctions on bicrystal substrates and the smaller contribution of the noise of SQUID control electronics to the total noise of the measurement system have led to the preferred utilization of bicrystal junctions in high-T c DC SQUIDs The grain boundary of the YBCO bicrystal junctions behaves as if it were mostly dielectric with an average barrier thickness t ≈ 2 nm (Winkler et al, 1994) and dielectric constant ε ≈ 28 for the grain boundary region in YBCO (Navacerrada, 2008). Both the noise parameter Γ and the Stewart-McCumber parameter C β contribute to the voltage noise of the Josephson junctions (Voss, 1981) and, consequently, to the magnetic field resolution of the DC SQUID magnetometers.…”