Frustration phenomena in Josephson junction arrays on a dice lattice

TL;DR

This study investigates how the unique geometry of dice lattice Josephson junction arrays influences their magnetic response, revealing unconventional phenomena linked to frustration and vortex states.

Contribution

It provides experimental evidence of frustration effects and vortex states in dice lattice Josephson arrays, connecting these findings to recent theories on accidental degeneracy.

Findings

Prominent peaks at f=1/3 and f=1/6 indicating vortex states with high phase coherence

Deep minimum at f=1/2 showing suppressed phase coherence

Observation of unconventional behavior due to interplay of frustration and geometry

Abstract

AC magnetoimpedance measurements performed on proximity-effect coupled Josephson junction arrays on a dice lattice reveal unconventional behaviour resulting from the interplay between the frustration f created by the applied magnetic field and the particular geometry of the system. While the inverse magnetoinductance exhibits prominent peaks at f=1/3 and at f=1/6 (and weaker structures at f=1/9,2/9,1/12,...) reflecting vortex states with a high degree of superconducting phase coherence, the deep minimum at f=1/2 points to a state in which the phase coherence is strongly suppressed. These observations are discussed at the light of recent theoretical work in which the concept of accidental degeneracy plays a central role.