“…For such a system, an extended JC model including atomic centre of mass motion and a standing wave coupling has been studied in a large number of papers, here we just mention a few. The dynamics has been analysed in, for example, [24,25,26,27,28,29,30,31,32,33], while in [30,31,32,33], approximation methods are used, such as Raman-Nath, Bragg, tight-binding or large detuning. In the Raman-Nath approximation, the kinetic energy term is neglected, and this has been assumed in Refs.…”