Pre-Floquet states facilitating coherent subharmonic response of periodically driven many-body systems

Abstract: We demonstrate coherent subharmonic motion of a many-Boson system subjected to an external time-periodic driving force. The underlying mechanism is exemplified numerically through analysis of a periodically driven Bose-Hubbard dimer, and clarified conceptually by semiclassical re-quantization of invariant tubes pertaining to the system's mean-field description. It is argued that even high-order subharmonic response can be systematically engineered, and be observed experimentally, with weakly interacting Floquet condensates comprising a sufficiently large number of particles.