Generation of Dark-Bright Soliton Trains in Superfluid-Superfluid Counterflow

TLDR

The dynamics of two penetrating superfluids exhibit an intriguing variety of nonlinear effects. The study investigates counterflow between two distinguishable components of a Bose‑Einstein condensate confined to a narrow channel. The dynamics are modeled by three‑dimensional numerical simulations of the coupled Gross‑Pitaevskii equations and analysis of density jumps between the flowing components. The experiment reveals trains of dark‑bright solitons produced by counterflow, with modulational instability identified as the key mechanism.

Abstract

The dynamics of two penetrating superfluids exhibit an intriguing variety of nonlinear effects. Using two distinguishable components of a Bose-Einstein condensate, we investigate the counterflow of two superfluids in a narrow channel. We present the first experimental observation of trains of dark-bright solitons generated by the counterflow. Our observations are theoretically interpreted by three-dimensional numerical simulations for the coupled Gross-Pitaevskii equations and the analysis of a jump in the two relatively flowing components' densities. Counterflow-induced modulational instability for this miscible system is identified as the central process in the dynamics.