Robustness of the Kondo effect in a quantum dot coupled to Majorana zero modes

TL;DR

This paper investigates whether the Kondo effect can coexist with Majorana zero modes in a quantum dot system, revealing that the Kondo effect persists at low temperatures and can exhibit non-Fermi liquid behavior depending on coupling.

Contribution

It demonstrates through numerical and analytical methods that the Kondo effect remains robust in the presence of Majorana modes and can be tuned between different quantum regimes.

Findings

Kondo effect persists at low temperatures despite coupling to MZMs

Residual impurity entropy indicates non-Fermi liquid properties

Tuning the dot-MZM coupling controls quantum regime transitions

Abstract

The prospect of using semiconductor quantum dots as an experimental tool to distinguish Majorana zero modes (MZMs) from other zero-energy excitations such as Kondo resonances has brought up the fundamental question of whether topological superconductivity and the Kondo effect can coexist in these systems. Here, we study the Kondo effect in a quantum dot coupled to a metallic contact and to a pair of MZMs. We consider a situation in which the MBS are spin polarized in opposite directions. By using numerical renormalization-group calculations and scaling analysis of the renormalization group equations, we show that the Kondo effect takes place at low temperatures, regardless the coupling to the MZMs. Interestingly, we find that the Kondo singlet essentially decouples from the MZMs such that the residual impurity entropy can show local non-Fermi liquid properties characteristic of the single Majorana excitations. This offers the possibility of tuning between Fermi-liquid and non-Fermi-liquid regimes simply by changing the quantum dot-MZM couplings.