Avviso di Seminario
A Josephson phase battery
Prof.ssa R. Citro, Dr.ssa O. Durante, Dr. C. Guarcello
Dipartimento di Fisica E. R. Caianiello - Unisa
23/07/2020 - ore 12:00, aula Zoom
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A classical battery converts chemical energy into a persistent voltage bias that can power electronic circuits. Similarly, a phase battery is a quantum device that provides a persistent phase bias to the wave function of a quantum circuit. It represents a key element for quantum technologies based on phase coherence. Starting from the Josephson effect, we discuss the realization of a phase battery in a hybrid superconducting circuit. It consists of an n-doped InAs nanowire with unpaired-spin surface states, that is proximitized by Al superconducting leads. It has been found that the ferromagnetic polarization of the unpaired-spin states is efficiently converted into a persistent phase bias phi0 across the wire, leading to the anomalous Josephson effect. By applying an external in-plane magnetic field one can achieve continuous tuning of phi0, hence charging and discharging the quantum phase battery. A theoretical model consistent with the observed symmetries of the anomalous Josephson effect in the vectorial magnetic field is also presented. Our results demonstrate how the combined action of spin-orbit coupling and exchange interaction induces a strong coupling between charge, spin, and superconducting phase, which is able to break the phase rigidity of the system and produce a phase battery.