Lock-in to commensurate states induced by a periodic array of nanoscale anti-dots in Nb superconductor

TL;DR

This paper investigates how a periodic array of nanoscale anti-dots in a Nb superconductor induces lock-in to commensurate vortex states, revealing narrow magnetic field states and harmonic responses indicative of a Mott insulator-like phase.

Contribution

It demonstrates the existence of narrow commensurate states and harmonic generation in Nb superconductors with nanoscale anti-dot arrays, linking these phenomena to a Mott insulator-like locked state.

Findings

Narrow states with 1% width of the matching field are observed at commensurate points.

Pronounced harmonic generation occurs in response to ac magnetic field or current.

The anomalies are related to a locked commensurate state similar to a Mott insulator.

Abstract

We study the interactions of the vortex lattice with a periodic square array of holes in a superconducting Nb film. Using high resolution magnetic field measurements of electrical losses, extremely narrow states with a magnetic field width reaching 1% of the matching field value are found at the commensurate points. They are accompanied by pronounced harmonic generation in response to ac modulation of the magnetic field or current. We relate these sharp anomalies to a locked commensurate state of the Mott insulator type.