•Sergei Sharov1 und Andrei Zaikin2
1Institut für Theoretische Festkörperphysik, Universität Karlsruhe, 76128 Karlsruhe, Germany
2Forschungszentrum Karlsruhe, Institut für Nanotechnologie, 76021, Karlsruhe, Germany
It has been established both experimentally and theoretically that thermodynamic properties of small isolated superconducting islands and grains may strongly depend on the electron parity number. In the present work we investigate the influence of the parity effect on supercurrents in isolated superconducting nanorings interrupted by a quantum point contact(QPC) and threaded by the Aharonov-Bohm magnetic flux.
In order to evaluate superurrents in rings with even and odd total number
of electrons we employ the parity projected partition function formalism.
Our main results and observations are as follows: (a) the dependence of
the supercurrent on the external flux and temperature in both even and
odd canonical ensembles derived here may strongly deviate from that established
for the grand canonical ensemble, (b) at sufficiently low temperatures
supercurrents in rings with odd number of electrons are totally blocked
provided QPC has only one conducting mode and (c) this blocking effect
gets partially lifted in structures with several or many conducting modes.
We also discuss possible realizations of the above effects and demonstrate
that our predictions can be directly tested in modern experiments.