Anomalous negative magnetoresistance in quantum-dot Josephson junctions with Kondo correlations

TL;DR

This paper reports the observation of anomalous negative magnetoresistance in quantum-dot Josephson junctions with Kondo correlations, linking vortex physics to supercurrent behavior and revealing new insights into quantum dot-superconductor interactions.

Contribution

It demonstrates the emergence of negative magnetoresistance due to vortex-induced quasiparticle trapping in Kondo-regime Josephson junctions, a novel phenomenon in this context.

Findings

Zero-bias conductance peak appears in Kondo regime

Negative magnetoresistance observed at weak magnetic fields

Vortex trapping enhances Josephson current

Abstract

The interplay between superconductivity and the Kondo effect has stimulated significant interest in condensed matter physics. They compete when their critical temperatures are close and can give rise to a quantum phase transition that can mimic Majorana zero modes. Here, we have fabricated and measured Al-InSb nanowire quantum dot-Al devices. In the Kondo regime, a supercurrent- induced zero-bias conductance peak emerges. This zero-bias peak shows an anomalous negative magnetoresistance (NMR) at weak magnetic fields. We attribute this anomalous NMR to quasi- particle trapping at vortices in the superconductor leads as a weak magnetic field is applied. The trapping effect lowers the quasiparticle-caused dissipation and thus enhances the Josephson current. This work connects the vortex physics and the supercurrent tunneling in Kondo regimes and can help further understand the physics of Josephson quantum dot system.