Electronic Structure in Mesoscopic Superconducting Disks

K. Tanaka, I. Robel and B. Jankó

Recent experiments on Al disks reveal unusual properties, such as the paramagnetic Meissner effect or peculiar phase transitions. Theoretical studies of these systems so far have been limited to the phenomenological Ginzburg-Landau framework.

To get a deeper insight into the behavior of these nanoscale systems, a microscopic analysis is necessary. In this work we perform microscopic, self-consistent calculations within the Bogoliubov-de Gennes formalism.

We show below the differential conductance for a giant vortex of 4 flux quanta. A new feature here compared to an isolated vortex in a bulk system is the presence of the oscillations above the gap energy. These are the so-called Tomasch oscillations, arising from the interference of quasiparticle amplitudes.

This feature is present also in a model system of a 2D disk with finite normal core and constant order parameter outside the core. Generally for quantum giant vortex states the local density of states (LDOS) exhibits peaks at the vortex core due to branches of bound states as a function of angular momentum.

For details, see PNAS 99, 5233 (2002).