Interplay between Kondo and Majorana interactions in quantum dots

TL;DR

This paper explores how Kondo and Majorana interactions influence a quantum dot coupled to a topological superconductor, revealing a new fixed point with unique correlations and measurable signatures.

Contribution

It introduces a comprehensive analysis of the interplay between Kondo and Majorana couplings, identifying a novel fixed point and its observable effects in quantum dot systems.

Findings

Identification of a new fixed point dominated by Majorana interactions

Distinct features in tunneling conductance and spin susceptibility

Presence of non-trivial correlations between dot spin and fermion parity

Abstract

We study the properties of a quantum dot coupled to a one-dimensional topological superconductor and a normal lead and discuss the interplay between Kondo and Majorana-induced couplings in quantum dot. The latter appears due to the presence of Majorana zero-energy modes localized at the ends of the one-dimensional superconductor. We investigate the phase diagram of the system as a function of Kondo and Majorana interactions using a renormalization-group analysis, a slave-boson mean-field theory and numerical simulations using the density-matrix renormalization group method. We show that, in addition to the well-known Kondo fixed point, the system may flow to a new fixed point controlled by the Majorana-induced coupling which is characterized by non-trivial correlations between a localized spin on the dot and the fermion parity of the topological superconductor and normal lead. We compute several measurable quantities such as differential tunneling conductance and impurity spin susceptibility which highlight some peculiar features characteristic to the Majorana fixed point.