Ac. Mota et al., COHERENT PHENOMENA IN MESOSCOPIC CYLINDERS OF CU AND AG IN PROXIMITY WITH A SUPERCONDUCTOR, Physica. B, Condensed matter, 197(1-4), 1994, pp. 95-100
Copper and silver cylinders driven to superconductivity by the proximi
ty effect show a novel form of quantum coherence. Below a characterist
ic temperature T(min), the induced diamagnetic currents in Cu and Ag d
ecrease as the temperature is reduced. The diamagnetic current is rest
ored by the application of a small magnetic field H < 10 Oe. For T < T
(min) the condition K(N)-1 greater-than-or-equal-to L is fulfilled and
the magnetic response can be described by DELTA(chi) = A exp(K(N)-1/L
). Here K(N)-1 is the decay length of the induced pair amplitude and L
the perimeter of the cylinder. We interpret this reentrant behaviour
as resulting from a paramagnetic persistent current which opposes the
diamagnetic Meissner current. Strong similarities between this novel m
agnetic response and persistent currents in mesoscopic normal metal ri
ngs are found.