Josephson ϕ0-junction in nanowire quantum dots

By D. Szombati, S. Nadj-Perge, D. Car, S. Plissard, E. Bakkers, L. Kouwenhoven. Nature Physics, 2015

249 citations recorded by the source corpus.

A so-called Josephson ϕ0-junction based on a nanowire quantum dot is reported. By means of electrostatic gating, it is possible to controllably introduce a phase offset taking any value between 0 and π in the ground state of the junction. The Josephson effect describes supercurrent flowing through a junction connecting two superconducting leads by a thin barrier1. This current is driven by a superconducting phase difference ϕ between the leads. In the presence of chiral and time-reversal symmetry of the Cooper pair tunnelling process2, the current is strictly zero when ϕ vanishes. Only if these underlying symmetries are broken can the supercurrent for ϕ = 0 be finite3,4,5. This corresponds to a ground state of the junction being offset by a phase ϕ0, different from 0 or π. Here, we report such a Josephson ϕ0-junction based on a nanowire quantum dot. We use a quantum interferometer device to investigate phase offsets and demonstrate that ϕ0 can be controlled by electrostatic gating. Our results may have far-reaching implications for superconducting flux- and phase-defined quantum bits as well as for exploring topological superconductivity in quantum dot systems.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics

View Paper: https://www.semanticscholar.org/paper/b988f278479dea94969227a30122345261e4f91f