Classical momentum diffusion in double-{delta}-kicked particles
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)
We investigate the classical chaotic diffusion of atoms subjected to pairs of closely spaced pulses ('kicks') from standing waves of light (the 2{delta}-KP). Recent experimental studies with cold atoms implied an underlying classical diffusion of a type very different from the well-known paradigm of Hamiltonian chaos, the standard map. The kicks in each pair are separated by a small time interval {epsilon}<<1, which together with the kick strength K, characterizes the transport. Phase space for the 2{delta}-KP is partitioned into momentum 'cells' partially separated by momentum-trapping regions where diffusion is slow. We present here an analytical derivation of the classical diffusion for a 2{delta}-KP including all important correlations which were used to analyze the experimental data. We find an asymptotic (t{yields}{infinity}) regime of 'hindered' diffusion: while for the standard map the diffusion rate, for K>>1, D{approx}K{sup 2}/2[1-2J{sub 2}(K){center_dot}{center_dot}{center_dot}] oscillates about the uncorrelated rate D{sub 0}=K{sup 2}/2, we find analytically, that the 2{delta}-KP can equal, but never diffuses faster than, a random walk rate. We argue this is due to the destruction of the important classical 'accelerator modes' of the standard map. We analyze the experimental regime 0.1 < or approx. K{epsilon} < or approx. 1, where quantum localization lengths L{approx}({Dirac_h}/2{pi}){sup -0.75} are affected by fractal cell boundaries. We find an approximate asymptotic diffusion rate D{proportional_to}K{sup 3}{epsilon}, in correspondence to a D{proportional_to}K{sup 3} regime in the standard map associated with the 'golden-ratio' cantori.
- OSTI ID:
- 20860803
- Journal Information:
- Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Vol. 74, Issue 2; Other Information: DOI: 10.1103/PhysRevE.74.026210; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-651X
- Country of Publication:
- United States
- Language:
- English
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