5 research outputs found
Proximity-induced screening and its magnetic breakdown in mesoscopic hybrid structures
We derive a general microscopic expression for the non-linear diamagnetic
current in a clean superconductor-insulator-normal metal structure with an
arbitrary interface transmission. In the absence of electron-electron
interactions in the normal metal the diamagnetic response increases
monotonously with decreasing temperature showing no sign of paramagnetic
reentrance down to T=0. We also analyze the magnetic breakdown of proximity
induced Meissner screening. We demonstrate that the magnetic breakdown field
should be strongly suppressed in the limit of small interface transmissions
while the linear diamagnetic current does not depend on the transmission of the
insulating barrier at low enough temperatures.Comment: 7 pages, 2 figure
Overscreening Diamagnetism in Cylindrical Superconductor-Normal Metal-Heterostructures
We study the linear diamagnetic response of a superconducting cylinder coated
by a normal-metal layer due to the proximity effect using the clean limit
quasiclassical Eilenberger equations. We compare the results for the
susceptibility with those for a planar geometry. Interestingly, for
the cylinder exhibits a stronger overscreening of the magnetic field, i.e., at
the interface to the superconductor it can be less than (-1/2) of the applied
field. Even for , the diamagnetism can be increased as compared to the
planar case, viz. the magnetic susceptibility becomes smaller than
-3/4. This behaviour can be explained by an intriguing spatial oscillation of
the magnetic field in the normal layer
The excitation spectrum of mesoscopic proximity structures
We investigate one aspect of the proximity effect, viz., the local density of
states of a superconductor-normal metal sandwich. In contrast to earlier work,
we allow for the presence of an arbitrary concentration of impurities in the
structure. The superconductor induces a gap in the normal metal spectrum that
is proportional to the inverse of the elastic mean free path l_N for rather
clean systems. For a mean free path much shorter than the thickness of the
normal metal, we find a gap size proportional to l_N that approaches the
behavior predicted by the Usadel equation (diffusive limit). We also discuss
the influence of interface and surface roughness, the consequences of a
non-ideal transmittivity of the interface, and the dependence of our results on
the choice of the model of impurity scattering.Comment: 7 pages, 8 figures (included), submitted to PR
Ring-shaped Andreev billiards in quantizing magnetic fields.
We present a detailed semiclassical study of a clean disk-shaped insulator–normal-metal–superconductor hybrid system in a magnetic field. It is based on an exact secular equation that we derived within the microscopic Bogoliubov–de Gennes (BdG) formalism. Results obtained from a classification of electron and hole orbits are in excellent agreement with those from an exact numerical diagonalization of the BdG equation. Our analysis opens up different possibilities for determining thermodynamic properties of mesoscopic hybrid systems