Self-trapping of excitations: Two-dimensional quasiparticle solitons in an extended Bose-Hubbard dimer array

Considering a two-dimensional (2D) Bose-Hubbard spinor lattice with weak nearest-neighbor interactions and no particle transfer between sites, we theoretically study the transport of energy from one initially excited dimer to the rest of the lattice. Beyond a critical interaction strength, low-energy on-site excitations are quickly dispersed throughout the array, while stronger excitations are self-trapped, resulting in localized energy breathers and solitons. These structures are quasiparticle analogs to the discrete 2D solitons in photonic lattices. Full many-body simulations additionally demonstrate the localization of one-particle entropy.