Speaker
Description
Localized nonlinear excitations can form long‑lived bound states whose internal degrees of freedom shape their dynamics. I will present two complementary mechanisms for binding solitary waves in two‑component Bose-Einstein condensates and their consequences for localization dynamics.
In miscible, nondipolar mixtures, polarization (“magnetic”) solitons interact via an effective potential that supports soliton molecules. This framework identifies the conditions for binding and yields an analytic dissociation energy for oppositely polarized pairs, in agreement with full dynamical simulations.
In dipolar mixtures, a roton minimum of the spin excitation branch induces intersoliton forces that oscillate with separation between dark-antidark pairs. The resulting periodic potential supports multiple bound states at distinct separations and generates spatial spin‑density oscillations around individual solitons—both direct signatures of the spin roton. In collisions, dipolar interactions enforce universal low‑velocity bouncing, contrasting with the transmit‑or‑bounce behavior of nondipolar solitons, offering a realistic path to confirming spin rotons experimentally.
These results show how soft spin modes and spin polarization mediate controllable long‑range forces that organize the binding and scattering of localized waves.
• R. M. V. Röhrs, Chunlei Qu and R. N. Bisset
Phys. Rev. A 112, 053316 (2025)
• R. M. V. Röhrs and R. N. Bisset
Phys. Rev. A 113, 033311 (2026)