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Taking a Look at Superconductors

Decent Essays
In the sixties, Kulik had used the mechanism of Andreev reflection to explain how a metal carries dissipation-less current between two superconductors.
Andreev later discovered that an electron incident on a superconductor with energy lying within the gap region gets reflected as a hole, which is the basic essence of Andreev reflection. \\
A charge of 2e is lost in the process which gets absorbed into the superconductor as a Cooper pairs.
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The same process occurs for a hole as an incident particle; in this case, the reflected particle will be an electron and the Cooper pair absorbed by the superconductor with be formed by two holes.\\
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An important application of Andreev reflection is in the study of tunneling of Cooper pairs in a Josephson Junction.
The transmission of Cooper pairs from one superconductor to another can be understood by considering the reflection of an eletron and hole into each other at the boundaries of the two superconductors.

This leads to conversion of normal current into dissipationless supercurrent. This supercurrent varies sinusoidally with the phase difference of the two superconductors and attains a maximum at the critical value of current which can flow through the junction.\\
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If an external magnetic field is applied to the barrier region of the junction, it alters the phases of the two superconductor, so that their net phase difference remains gauge-invariant. As a consequence, the current through the junction also gets modified in the
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