Quantum mechanics of superconducting nanowires

TL;DR

This paper models quantum phase slips in superconducting nanowires as a quantum mechanical system with linearly interacting charges, revealing behaviors akin to insulators and predicting multiple energy bands and exciton modes.

Contribution

It introduces a new quantum mechanical framework for phase slips in nanowires, highlighting their interactions and resulting energy band structures.

Findings

High-density phase slip states behave as insulators at low temperatures.

Quantum phase slips create multiple energy bands in the system.

An interband exciton mode arises from phase slip interactions.

Abstract

In a short superconducting nanowire connected to bulk superconducting leads, quantum phase slips behave as a system of linearly (as opposed to logarithmically) interacting charges. This system maps onto quantum mechanics of a particle in a periodic potential. We show that, while the state with a high density of phase slips is not a true insulator (a consequence of Josephson tunneling between the leads), for a range of parameters it behaves as such down to unobservably small temperatures. We also show that quantum phase slips give rise to multiple branches (bands) in the energy-current relation and to an interband ("exciton") mode.