# Well-defined Fano effect in the Andreev reflection process of a parallel double-quantum-dot structure

## TL;DR

This paper explores how Fano interference manifests in Andreev reflection within a double-quantum-dot system coupled to a superconductor, revealing tunable Fano lineshapes and complex interference effects.

## Contribution

It demonstrates the presence and tunability of Fano lineshapes in Andreev reflection, highlighting the complex interference mechanisms unique to this process.

## Key findings

- Fano lineshapes appear in the conductance spectrum of Andreev reflection.
- Fano interference can be reversed by tuning dot levels or magnetic flux.
- The Fano effect in this context exhibits unique properties compared to normal tunneling.

## Abstract

We investigate the Andreev reflection in the parallel double-quantum-dot structure, by considering one metallic lead and one $s$-wave superconductor to couple to the quantum dots simultaneously. It is found that the Fano lineshhape has opportunities to appear in the linear conductance spectrum of the Andreev reflection, which can be reversed by tuning the dot level or local magnetic flux. However, the property of the Fano effect is very complicated, in comparison with the normal electron tunnelling case. This is manifested as the special Fano form of the linear-conductance expression and the interference manner among the Feynman paths. We believe that this work can be helpful for understanding the Fano interference in the Andreev reflection process.