Multi-Terminal Coulomb-Majorana Junction

TL;DR

This paper investigates how finite charging energy influences the low-energy physics of a multi-terminal Majorana junction, revealing a transition from decoupled wires to an exotic Kondo fixed point driven by interactions.

Contribution

It introduces the impact of weak finite charging energy on Majorana junctions, showing the emergence of a Kondo fixed point and destabilization of the Andreev fixed point.

Findings

Weak charging energy can induce a Kondo fixed point.

Strong charging energy decouples the wires.

Interactions destabilize the ideal Andreev reflection.

Abstract

We study multiple helical nanowires in proximity to a common mesoscopic superconducting island, where Majorana fermion bound states are formed. We show that a weak finite charging energy of the center island may dramatically affect the low-energy behavior of the system. While for strong charging interactions, the junction decouples the connecting wires, interactions lower than a non-universal threshold may trigger the flow towards an exotic Kondo fixed point. In either case, the ideally Andreev reflecting fixed point characteristic for infinite capacitance (grounded) devices gets destabilized by interactions.