Magnetic solitons in binary mixtures of Bose–Einstein condensates

Huan Zhang, Ming Gong, Jingsong He +1 more

Xiao Chai, Di Lao, Kazuya Fujimoto +2 more

Röhrs, Rene

In this thesis, we investigate polarised solitary waves, known as magnetic solitons and dark-antidark solitons, in binary (two-component) Bose-Einstein condensates in the miscible phase. These solitons have been recently realised in experiments and are predicted to form bound states. We calculate the interaction potentials between magnetic solitons with the same and opposite polarisation, uncovering the mechanisms underlying bound state formation. By considering two superimposed counter-propagating magnetic solitons with opposite polarisation, we analytically calculate the dissociation energy of the bound states and find good agreement with full numerical simulations. Furthermore, we show that the oscillation period of bound states depends on the maximum soliton separation. We subsequently extend these results to dark-antidark solitons. For binary dipolar Bose- Einstein condensates, we derive the dispersion relation of elementary excitations and find that, in the presence of a spin-roton, spin-density modulations form around dark-antidark solitons. These modulations lead to additional local maxima and minima in the inter-soliton potentials, enabling the formation of additional bound state regions. Additionally, we compare the collision characteristics of magnetic solitons in non-dipolar systems with dark-antidark solitons in dipolar–nondipolar condensate mixtures and explore the collisions between bound states in the non-dipolar case.

Stéphane Coen, Marc Haelterman

The structure and dynamics of the domain walls separating segregated condensates in trapped mixtures of repulsive Bose-Einstein condensates are studied. Our work reveals that, under fairly general conditions, these domain walls behave as independent dynamical entities, which allows us to identify them as constituting a novel class of multicomponent solitons in Bose-Einstein condensates.

Di Lao, Xiao Chai, Kazuya Fujimoto +3 more

A. Farolfi, Dimitrios Trypogeorgos, Carmelo Mordini +2 more

We experimentally investigate the dynamics of spin solitary waves (magnetic solitons) in a harmonically trapped, binary superfluid mixture. We measure the in situ density of each pseudospin component and their relative local phase via an interferometric technique we developed and as such, fully characterize the magnetic solitons while they undergo oscillatory motion in the trap. Magnetic solitons exhibit nondispersive, dissipationless longtime dynamics. By imprinting multiple magnetic solitons in our ultracold gas sample, we engineer binary collisions between solitons of either the same or opposite magnetization and map out their trajectories.