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Quantal Andreev Maps: A New Paradigm of Quantum Chaos in Superconductivity
Philippe Jacquod
Leiden University
During the past two decades, one-dimensional quantum mechanical maps have
developed into one of two paradigms of quantum chaos, the other paradigm
being the two-dimensional billiard. These two paradigms share a common set
of phenomena in the fields of quantum chaos and localization.
The combination of chaos and superconductivity produces an entirely
new phenomenology, notably the appearance of an excitation gap as a
signature of quantum chaos. The paradigm common to most of the literature
is the two-dimensional billiard connected to a superconductor, a constriction
usually referred to as an "Andreev billiard".
My talk will be devoted to the construction of a second paradigm of quantum
chaos in presence of superconductivity: quantum maps with particle-hole
conversion (Andreev reflection) and particle-hole symmetry. I will show
that the resulting "Andreev maps" exhibit the same excitation gap as quantum
dots in the proximity to a superconductor, and check competing analytical
predictions of random-matrix theory and semiclassical chaos - in particular,
the logarithmic reduction of the quasiparticle gap when the Lyapunov
exponent and/or the effective Planck constant are small enough, that
the quantum ergodicity time - the "Ehrenfest" time - becomes comparable
to the quasiparticle dwell time.
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