The role of quasi-momentum in the resonant dynamics of the atom–optics kicked rotor

We examine the effect of the initial atomic momentum distribution on the dynamics of the atom–optical realisation of the quantum kicked rotor. The atoms are kicked by a pulsed optical lattice, the periodicity of which implies that quasi–momentum is conserved in the transport problem. We study and compare experimentally and theoretically two resonant limits of the kicked rotor: in the vicinity of the quantum resonances and in the semiclassical limit of vanishing kicking period. It is found that for the same experimental distribution of quasi–momenta, significant deviations from the kicked rotor model are induced close to quantum resonance, while close to the classical resonance (i.e. for small kicking period) the effect of the quasimomentum vanishes. PACS numbers: 42.50.Vk,32.80.Qk,05.45.Mt,05.60.-k