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The theory of the reentrant effect in susceptibility of cylindrical mesoscopic samples
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The theory of the reentrant effect in susceptibility of cylindrical mesoscopic samples
Тема:
Специальный выпуск superconductivity: XX years after the discovery
Інший ID:
PACS: 74.50.+r, 74.45.+c
Посилання:
The theory of the reentrant effect in susceptibility
of cylindrical mesoscopic samples / G.A. Gogadze // Физика низких температур. — 2006. — Т. 32, № 6. — С. 716–728. — Бібліогр.: 29 назв. — англ.
Підтримка:
The author is sincerely grateful to A.N. Omelyanchouk
for helpful discussions and support, to S.I.
Shevchenko for valuable comments. I am indebted to
I.O. Kulik for reading through the text and useful
comments.
Дата:
2006
Переглядів:
743
Завантажень:
383
Анотація:
A theory has been developed to explain the anomalous behavior of the magnetic susceptibility
of a normal metal-superconductor (NS) structure in weak magnetic fields at millikelvin temperatures.
The effect was discovered experimentally (A.C. Mota et al., Phys. Rev. Lett. 65, 1514
(1990)). In cylindrical superconducting samples covered with a thin normal pure metal layer, the
susceptibility exhibited a reentrant effect: it started to increase unexpectedly when the temperature
lowered below 100 mK. The effect was observed in mesoscopic NS structures when the N and S
metals were in good electric contact. The theory proposed is essentially based on the properties of
the Andreev levels in the normal metal. When the magnetic field (or temperature) changes, each
of the Andreev levels coincides from time to time with the chemical potential of the metal. As a result,
the state of the NS structure experiences strong degeneracy, and the quasiparticle density of
states exhibits resonance spikes. This generates a large paramagnetic contribution to the susceptibility,
which adds up to the diamagnetic contribution thus leading to the reentrant effect. The explanation
proposed was obtained within the model of free electrons. The theory provides a good
description for experimental results.
