Excitation of Moving Discrete Breathers in Square β-FPUT Lattice by External Driving

A discrete breather (DB) is a spatially localized, large-amplitude vibrational mode in a defect-free nonlinear lattice. The discovery of DBs raised the question of how they can be excited in nonlinear lattices. One possible mechanism is supratransmission, whereby energy is transferred to the lattice from an external source at a frequency outside the phonon spectrum of the lattice. When the amplitude of the external driving is large enough, the DBs are excited and transfer energy to the lattice. In a recent study, we analyzed the supratransmission effect for the β-FPUT square lattice and demonstrated that DBs can be emitted from a pair of periodically driven particles along close-packed directions. The present work demonstrates that DBs can also be excited along the diagonal directions of the lattice. The results confirm the existence of moving DBs propagating either along a close-packed direction or a diagonal direction in the square lattice. This finding is significant because it reveals the mechanisms of energy transport in a square lattice via nonlinear excitations.