Conductance enhancement due to the resonant tunneling into the subgap vortex core states in normal metal/superconductor ballistic junctions

TL;DR

This paper demonstrates that magnetic vortices in a superconductor can significantly enhance conductance in a ballistic junction by resonant tunneling into vortex core states, offering a new way to probe vortex properties.

Contribution

It reveals how subgap vortex core states cause resonant conductance enhancement in normal metal/superconductor junctions under magnetic fields, using Bogolubov-de Gennes theory.

Findings

Resonant enhancement of Andreev reflection due to vortex core states.

Conductance increase depends on vortex distance to the junction.

Magnetic field controls the vortex-induced conductance effects.

Abstract

We investigate the low-energy quantum transport in the ballistic normal metal-insulator -superconductor junction in the presence of magnetic field creating Abrikosov vortices in the superconductor. Within the Bogolubov- de Gennes theory we show that the presence of the subgap quasiparticle states localized within the vortex cores near the junction interface leads to the strong resonant enhancement of the Andreev reflection probability, and the normal-to supercurrent conversion. The corresponding increase of the charge conductance of the junction is determined by the distance from the vortex chain to the junction interface, which can be controlled by the applied magnetic field. The effect that we study provides a tool for probing the vortex core states by the measurements of charge transport across the applied magnetic field.