Environmental Coulomb blockade of topological superconductor-normal metal junctions

TL;DR

This paper investigates charge transport in topological superconductor-normal metal junctions with Majorana bound states, revealing temperature-independent conductance due to resonant Andreev reflections across different tunneling regimes.

Contribution

It extends previous work by analyzing Majorana bound states coupled to metallic dots in both weak and strong tunneling regimes, including non-perturbative effects and gate-voltage modulation.

Findings

Conductance remains temperature independent due to resonant Andreev reflections.

Different tunneling regimes show distinct charge transport behaviors.

Majorana bound states enable non-perturbative cotunneling effects.

Abstract

We study charge transport of a topological superconductor connected to different electromagnetic environments using a low-energy description where only the Majorana bound states in the superconductor are included. Extending earlier findings who found a crossover between perfect Andreev reflection with conductance $2e^2/h$ to a regime with blocked transport when the resistance of the environment is larger than $2e^2/h$, we consider Majorana bound states coupled to metallic dots. in particular, we study two topological superconducting leads connected by a metallic quantum dot in both the weak tunneling and strong tunneling regimes. For weak tunneling, we project onto the most relevant charge states. For strong tunneling, we start from the Andreev fixed point and integrate out charge fluctuations which gives an effective low-energy model for the non-perturbative gate-voltage modulated cotunneling current. In both regimes and in contrast to cotunneling with normal leads, the conductance is temperature independent because of the resonant Andreev reflections, which are included to all orders.