Tunable interplay between superconductivity and correlations in nanoscopic heterostructures

Abstract

Artificial heterostructures consisting of the superconducting electrode(s) and the free electron reservoir(s) interconnected through various nanoscopic objects, like: quantum dots, nanowires or molecules enable a fully controllable confrontation of the correlation effects with electron pairing. Discrete energy spectrum of the nanoscopic objects (due to the quantum size effect) strongly depends on the many-body effects. Via the proximity effect, these nanoscopic objects are converted into the superconducting grains. Since the coupling to external electrodes can be varied experimentally, this enables a fully controllable investigation of an interplay between the electron correlations and superconductivity. In this work, we explore the subgap (Shiba) states arising from the induced pairing and analyse their influence on the Kondo-type correlations. This issue is currently widely explored using various nanoscopic devices.

Keywords:

• proximity effect
• Shiba states
• electron correlations
• Kondo effect

Acknowledgements

We acknowledge discussions with Johannes Bauer and Karol I. Wysokiński.