Current and potential distributions in highly anisotropic superconductors with inclusions

Autor: A.E. Curzon, S. Gygax, Fathalla Hamed
Rok vydání: 1997
Předmět:
Zdroj: Physica C: Superconductivity. 292:189-196
ISSN: 0921-4534
Popis: Thin whiskers of orthorhombic Bi 2 Sr 2 Ca 1 Cu 2 O x have been grown from powders and their resistive transitions have been studied at constant current. The potential difference between the voltage electrodes on some of the whiskers showed an abrupt increase when they were cooled below ∼ 105 K. It is shown that this increase may be explained by one or more intercalated layers of superconducting Bi 2 Sr 2 Ca 2 Cu 3 O x inside the bulk Bi 2 Sr 2 Ca 1 Cu 2 O x material. The whisker is represented by an orthorhombic solid which extends from − ∞ to +∞ in the b -direction and has a thickness in the c -direction which is much less than the length in the a -direction. The ratio of the electrical conductivities σ aa σ cc is taken to be of the order of 10 4 as is the case for Bi 2 Sr 2 Ca 1 Cu 2 O x . The two-dimensional potential distribution in the whisker satisfies Laplace's equation in a co-ordinate system in which the displacements along the c -direction are scaled by a factor of √( σ aa σ cc ). This equation is solved by a standard relaxation method. Two cases have been considered. In the first, the entire crystal is in its normal state and in the second there is an intercalated superconducting layer of Bi 2 Sr 2 Ca 2 Cu 3 O x perpendicular to the c -direction and inside normally conducting Bi 2 Sr 2 Ca 1 Cu 2 O x which constitutes the bulk material. It is this layer which gives rise to the observed anomalous resistive transitions at 105 K and to changes in potential distributions. Figures are presented to illustrate the changes.
Databáze: OpenAIRE
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