Observation of Breathers in Josephson Ladders

TLDR

Whirling states persist under a spatially homogeneous bias current in Josephson ladders. We visualized these states with low‑temperature scanning laser microscopy, computed accurate breather solutions, and performed stability analysis to interpret I‑V patterns. We observed spatially localized excitations (breathers) in a ladder of small Josephson junctions.

Abstract

We report on the observation of spatially localized excitations in a ladder of small Josephson junctions. The excitations are whirling states which persist under a spatially homogeneous force due to the bias current. These states of the ladder are visualized using a low temperature scanning laser microscopy. We also compute breather solutions with high accuracy in corresponding model equations. The stability analysis of these solutions is used to interpret the measured patterns in the I-V characteristics.