Dr. Mikhail A. Skvortsov

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We study the superconducting proximity effect in a quantum wire with
broken time-reversal (TR) symmetry connected to a superconductor. We
consider the situation of a strong TR-symmetry breaking, so that
Cooper pairs entering the wire from the superconductor are immediately
destroyed. Nevertheless, some traces of the proximity effect survive:
for example, the local electronic density of states (LDOS) is
influenced by the proximity to the superconductor, provided that
localization effects are taken into account. With the help of the
supersymmetric sigma model, we calculate the average LDOS in such a
system. The LDOS in the wire is strongly modified close to the
interface with the superconductor at energies near the Fermi
level. The relevant distances from the interface are of the order of
the localization length, and the size of the energy window around the
Fermi level is of the order of the mean level spacing at the
localization length. Remarkably, the sign of the effect is sensitive
to the way the TR symmetry is broken: In the spin-symmetric case
(orbital magnetic field), the LDOS is depleted near the Fermi energy,
whereas for the broken spin symmetry (magnetic impurities), the LDOS
at the Fermi energy is enhanced.

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Landau Institute of Theoretical Physics, Chernogolovka
Seminarraum Theoretische Physik
Contact: not specified