Kondo-Enhanced Andreev Tunneling in InAs Nanowire Quantum Dots

TL;DR

This paper investigates how Kondo correlations influence Andreev tunneling in InAs nanowire quantum dots with superconducting leads, revealing occupation-dependent conductance features and the interplay of many-body effects.

Contribution

It demonstrates the enhancement of Andreev tunneling peaks due to Kondo correlations in quantum dots, a novel observation in hybrid nanostructures.

Findings

Odd occupation shows stronger sub-gap peaks at |V_sd|=Δ/e.

Even occupation exhibits weaker sub-gap peaks.

Kondo correlations enhance Andreev tunneling in odd-occupied dots.

Abstract

We report measurements of the nonlinear conductance of InAs nanowire quantum dots coupled to superconducting leads. We observe a clear alternation between odd and even occupation of the dot, with sub-gap-peaks at $|V_{sd}|=\Delta/e$ markedly stronger(weaker) than the quasiparticle tunneling peaks at $|V_{sd}|=2\Delta/e$ for odd(even) occupation. We attribute the enhanced $\Delta$-peak to an interplay between Kondo-correlations and Andreev tunneling in dots with an odd number of spins, and substantiate this interpretation by a poor man's scaling analysis.