Electrical behavior of YBa2Cu3O7−x grain boundary junctions under low magnetic field (original) (raw)
Related papers
IEEE Transactions on Magnetics, 1991
We report on the superconducting transport characteristics of YBa2Cii307-6 grain boundary junctions (GBJs) fabricated by laser a.blation deposition on SrTi03 bicrystals. For narrow GBJs wit,li a. width smaller than about 4 times their Josephson penrl,rat,ion depth, the current-voltage characteristics can be modc.lcd closely by the resistively shunted junction (RSJ) model and thc magnetic field dependence of the critical current is Fraun-Iiofer pattern like. The temperature dependence of the critical currelit is proportional to (1-T/T,)' close to T,. The charackristic voltages V, = JEbpN, where JEb is the critical current tlrnsity and p~ the normal resistance times unit area of the GB.Js, range between 0.2 and 8mV at 4.2K and scale proporlioiial to (l / p~) '. ? The transport characteristics of the GBJs ai'e iii agreement with a SNINS-type junction model.
Magnetic field dependence of the critical current in YBa2Cu3O7−δ bicrystal grain boundary junctions
Applied Physics Letters, 1993
The magnetic field dependences of the critical-current of a granular s-wave superconductor has been determined by considering the rectangular and circular junction model of an array of small superconducting particles which interacting by Josephson coupling through insulating barriers. We will show that in the case of circular model, the maximum critical current of the Josephson current is larger than that of rectangular model.
Barrier properties in YBa2Cu3O7-x grain-boundary Josephson junctions using electron-beam irradiation
Physical Review B, 1998
Electron-beam irradiation has been used to induce controllable variations in the properties of YBa 2 Cu 3 O 7Ϫx biepitaxial grain-boundary Josephson junctions. A correlation between the transport properties and the microstructure was obtained by determining the ratio of a barrier thickness to the dielectric constant of the junctions with different barriers. These results give evidence of the role of the oxygen content and the dielectric constant of the interface region in transport phenomena. The experiment also demonstrates frequency tunability in a resonant soliton oscillator. ͓S0163-1829͑98͒51322-2͔
Mesoscopic conductance fluctuations in YBa2Cu3O7−δ grain boundary junctions at low temperature
Physical Review B, 2009
The magneto-conductance in YBCO grain boundary Josephson junctions, displays fluctuations at low temperatures of mesoscopic origin. The morphology of the junction suggests that transport occurs in narrow channels across the grain boundary line, with a large Thouless energy. Nevertheless the measured fluctuation amplitude decreases quite slowly when increasing the voltage up to values about twenty times the Thouless energy, of the order of the nominal superconducting gap. Our findings show the coexistence of supercurrent and quasiparticle current in the junction conduction even at high nonequilibrium conditions. Model calculations confirm the reduced role of quasiparticle relaxation at temperatures up to 3 Kelvin.
Electron Transport in High-Tc Superconducting Grain Boundary Junctions
1999
The current state and the prospects of the application of high-¹ superconducting grain boundary Josephson junctions in microwave electronics devices are given. It is approached by sketching the typical fabrication technique of the junction. Josephson bicrystal junctions on sapphire substrate are considered in detail. The results of dc microwave and magnetic measurements of YBCO bicrystal junctions on r-cut sapphire are presented. The junctions with high resistance 10}20 and I R , "1}2 mV and tolerance of R , S around 30% on the chip allow to create microwave circuits with low integration (up to 10 junctions on chip). The microwave dynamics of the junction with superconducting current-phase relation "ts with sin relation better than 5%, that clearly indicates the tunnel conductivity between two YBCO electrodes. It was found that critical current density depends on the square root of interface transparency in accordance with the prediction of superconducting current transport via Andreev's bound surface states. The speci"c properties of current transport in high-¹ grain boundary junctions with taking into account d-wave type of gap order in high-¹ superconductor are discussed.
Physical Review B, 2000
We have analyzed the electromagnetic properties of small and long YBa 2 Cu 3 O 7Ϫx grain-boundary Josephson junctions. The Swihart velocity increases with junction width ͑w͒ while the ratio of the relative dielectric constant to the barrier thickness (/t) decreases. We found that the product wϫ/t is approximately constant. These results have been explained in the framework of the filamentary model, where the barrier can be regarded as a disordered dielectric medium with a high density of superconducting filaments. Experiments demonstrate that a controllable variation of these parameters can be achieved by helium irradiation at 80 keV. We give examples of an enhancement of weak-link properties of junctions for doses in the range of 10 13 cm Ϫ2. Raising the dose we can sweep the modification of the weak-link properties from an increase of the junction critical current of about 10% to a severe degradation of the coupling energy of the barrier, although the superconducting properties of the electrodes always worsen gradually.
Observation of mesoscopic conductance fluctuations in YBa2Cu3O7−δ grain boundary Josephson junctions
Physical Review B - PHYS REV B, 2007
Magneto-fluctuations of the normal resistance R_N have been reproducibly observed in high critical temp erature superconductor (HTS) grain boundary junctions, at low temperatures. We attribute them to mesoscopic transport in narrow channels across the grain boundary line. The Thouless energy appears to be the relevant energy scale. Our findings have significant implications on quasiparticle relaxation and coherent transport in HTS grain boundaries.
Journal of Applied Physics, 2008
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.
The Relation Between Barrier Structure and Current Uniformity in YBCO Josephson Junctions
Electromagnetic transport measurements were combined with high-resolution electron microscopy observations to study the relation between structure and local critical currents in YBa 2 Cu 3 O 7−x (YBCO) Josephson junctions. The spatial variation of the critical current J (x) along the length of the boundary for interface engineered Josephson junctions and bicrystal grain boundary Josephson junctions was determined using a phase retrieval algorithm. The current distribution solutions were found to be highly uniform along the length of interface engineered junctions in contrast to solutions for grain boundary junctions. The latter showed significant spatial oscillations in the critical current as well as areas along the boundary that carried no current. Microstructural evaluation of interface engineered junctions fabricated using identical processing parameters to the junctions used for transport measurements suggest that the uniform current distribution is controlled by a highly uniform barrier layer formed between the superconducting electrodes. Microstructural evaluation of grain boundary junctions similar to the junctions used for transport measurements show considerable variations of the grain boundary structure within a single junction.