Critical currents, phase slip centers, and phase slip lines in superconducting films in the absence of external magnetic field

During last decade, considerable efforts were made to achieve coherent emission from stacks of many Josephson junctions. It is known that strong emission from a junction in the presence of external magnetic field appears at the so-called Fiske steps in the IV-characteristic at voltages which correspond to frequencies of geometrical resonances. However, it is possible to obtain resonant steps in long junctions without external magnetic field. The periodical movement of fluxons is excited due to some disorder in the distribution of critical currents along junctions. The so-called zero-field steps are formed in the IV-curve due to the interaction of fluxons with oscillations of voltage at Josephson frequencies. We investigated numerically IV-characteristics and the dependence of the average square of ac voltage at the end of the stack of two long Josephson junctions on the average voltage. Junctions interacted inductively with each other. We introduced not only the Gaussian distribution of critical currents along junctions but also the Gaussian distribution of coefficients of the interaction between junctions (mutual inductances). Zero-field steps in the IV-characteristic were found at voltages which corresponded to frequencies of in-phase collective modes in the stack as well as to frequencies of uncoupled junctions. Zero-field steps appeared in the hysteretic region of the IV-curve. There appeared also jumps of voltage from the resistive branch to the zero-field step. We showed that there existed distributions of mutual inductances along junctions which provided jumps to voltages at which the average square of ac voltage at the end of the stack (which is proportional to power of emission) was larger than that for the stack with the uniform distribution of mutual inductances.

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Температурные зависимости критических параметров неоднородных сверхпроводящих пленок

Физика твердого тела ◽

10.21883/ftt.2021.08.51150.076 ◽

2021 ◽

Vol 63 (8) ◽

pp. 1035

Author(s):

П.И. Безотосный ◽

К.А. Дмитриева

Keyword(s):

Magnetic Field ◽

Critical Temperature ◽

External Magnetic Field ◽

Critical Current Density ◽

Critical Current ◽

Current Density ◽

Superconducting Films ◽

Critical Magnetic Field ◽

Temperature Dependences ◽

Comparison Of The Results

The results of calculating the temperature dependences of the critical current density and critical magnetic field of thin inhomogeneous superconducting films are presented. Comparison of the results obtained for inhomogeneous films with the results of calculations for homogeneous ones showed that in both cases, the decrease in the critical magnetic field occurs according to the root law, and the critical current density changes according to a power law with a degree of 3/2 when approaching the critical temperature. Quantitatively, the critical current density for inhomogeneous films in the absence of an external magnetic field is lower than for homogeneous ones. In turn, the critical magnetic field of inhomogeneous films is much larger than the critical field of homogeneous films.

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Phase-slip centers of superconducting indium bridges with variable thickness in a magnetic field

Journal of Low Temperature Physics ◽

10.1007/bf00683456 ◽

1990 ◽

Vol 79 (1-2) ◽

pp. 55-65 ◽

Cited By ~ 1

Author(s):

Takahiro Yamamoto ◽

Takafumi Aomine

Keyword(s):

Magnetic Field ◽

Variable Thickness ◽

Phase Slip ◽

Phase Slip Centers

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Characterization of Bi2212 Superconductor Bulk Samples by Digital Image Processing

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.975.128 ◽

2014 ◽

Vol 975 ◽

pp. 128-133

Author(s):

Antonio Renato Bigansolli ◽

Tessie Gouvêa da Cruz ◽

Francisco Romário de Souza Machado ◽

Durval Rodrigues Jr.

Keyword(s):

Magnetic Field ◽

External Magnetic Field ◽

Analytical Techniques ◽

Critical Currents ◽

Weak Links ◽

Critical Temperatures ◽

Heat Treated ◽

Grain Distribution ◽

Superconductor Bulk

The use of superconductors of high critical temperatures in applied superconductivity leads to higher operation temperatures and economy of cryogenic fluids. High temperature superconductor materials exhibits limited transport properties due to grain boundary weak-links and anisotropy on the critical currents. The texturing development in these superconductors decreases in an efficient way the number of high-angle grain boundaries, increasing the values of critical current densities (Jc). In this research the size grain distribution characterization of Bi2212 superconductor bulk samples heat treated under the influence of an applied external magnetic field of 5T was carried out combining processing and images analysis obtained by SEM and statistical methodologies. The objective is to investigate influence of an external magnetic field applied during the heat treatment profiles on the texturing of Bi2Sr2CaCu2O8+δ (Bi2212) bulk by using complementary analytical techniques.

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