Critical Current 0-$\pi$ Transition in Designed Josephson Quantum Dot Junctions

TL;DR

This paper investigates the supercurrent behavior in quantum dot Josephson junctions, revealing gate-controlled 0-$$ transitions and providing precise measurements of the critical current.

Contribution

It introduces a design for quantum dot Josephson junctions optimized for supercurrent measurement and demonstrates gate-tunable 0-$$ transitions consistent with theoretical models.

Findings

Critical current exhibits strong gate modulation.

Zero crossing of critical current near resonance indicates 0-$$ transition.

Experimental results agree with theoretical predictions.

Abstract

We report on quantum dot based Josephson junctions designed specifically for measuring the supercurrent. From high-accuracy fitting of the current-voltage characteristics we determine the full magnitude of the supercurrent (critical current). Strong gate modulation of the critical current is observed through several consecutive Coulomb blockade oscillations. The critical current crosses zero close to, but not at, resonance due to the so-called 0-$\pi$ transition in agreement with a simple theoretical model.