Kondo Universal Scaling for a Quantum Dot Coupled to Superconducting Leads

TL;DR

This study demonstrates universal scaling behavior in a quantum dot system where the interplay between Kondo effect and superconductivity is tuned by magnetic fields, revealing a fundamental energy scale relationship.

Contribution

The paper provides experimental evidence for universal scaling of zero-bias conductance with the ratio of superconducting gap to Kondo temperature in a quantum dot system.

Findings

Zero-bias conductance collapses onto a single curve when scaled by Delta/kT_K.

Universal scaling holds across different Kondo valleys and magnetic field conditions.

Experimental validation of theoretical predictions for Kondo-superconductor interplay.

Abstract

We study competition between the Kondo effect and superconductivity in a single self-assembled InAs quantum dot contacted with Al lateral electrodes. Due to Kondo enhancement of Andreev reflections the zero-bias anomaly develops sidepeaks, separated by the superconducting gap energy Delta. For ten valleys of different Kondo temperature T_K we tune the gap Delta with an external magnetic field. We find that the zero-bias conductance in each case collapses onto a single curve with Delta/kT_K as the only relevant energy scale, providing experimental evidence for universal scaling in this system.