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Title: Symmetry and transport in a cold atom ratchet with multifrequency driving

Abstract

We analyze, both experimentally and via semiclassical Monte Carlo simulations, a cold atom ratchet with multifrequency driving. We investigate the relationship between symmetries and transport both in the case of a periodic driving and in the quasiperiodic limit. We also study quantitatively the line shape and linewidth of the ratchet current, and their dependence on the interaction parameters.

Authors:
; ;  [1]
  1. Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)
Publication Date:
OSTI Identifier:
20982548
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevA.75.053406; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ATOMS; COMPUTERIZED SIMULATION; INTERACTIONS; MONTE CARLO METHOD; PERIODICITY; SEMICLASSICAL APPROXIMATION; SYMMETRY; TEMPERATURE RANGE 0000-0013 K

Citation Formats

Gommers, R., Brown, M., and Renzoni, F. Symmetry and transport in a cold atom ratchet with multifrequency driving. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.053406.
Gommers, R., Brown, M., & Renzoni, F. Symmetry and transport in a cold atom ratchet with multifrequency driving. United States. doi:10.1103/PHYSREVA.75.053406.
Gommers, R., Brown, M., and Renzoni, F. Tue . "Symmetry and transport in a cold atom ratchet with multifrequency driving". United States. doi:10.1103/PHYSREVA.75.053406.
@article{osti_20982548,
title = {Symmetry and transport in a cold atom ratchet with multifrequency driving},
author = {Gommers, R. and Brown, M. and Renzoni, F.},
abstractNote = {We analyze, both experimentally and via semiclassical Monte Carlo simulations, a cold atom ratchet with multifrequency driving. We investigate the relationship between symmetries and transport both in the case of a periodic driving and in the quasiperiodic limit. We also study quantitatively the line shape and linewidth of the ratchet current, and their dependence on the interaction parameters.},
doi = {10.1103/PHYSREVA.75.053406},
journal = {Physical Review. A},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • Cold atoms in optical lattices have emerged as an ideal system to investigate the ratchet effect, as demonstrated by several recent experiments. In this work we analyze theoretically two aspects of ac-driven transport in cold-atom ratchets. We first address the issue of whether, and to what extent, an ac-driven ratchet for cold atoms can operate as a motor. We thus study theoretically a dissipative motor for cold atoms, as obtained by adding a load to a 1D nonadiabatically driven rocking ratchet. We demonstrate that a current can be generated also in the presence of a load, e.g., the ratchet devicemore » can operate as a motor. Correspondingly, we determine the stall force for the motor, which characterizes the range of loads over which the device can operate as a motor, and the differential mobility, which characterizes the response to a change in the magnitude of the load. Second, we compare our results for the transport in an ac-driven ratchet device with the transport in a dc-driven system. We observe a peculiar phenomenon: the double-harmonic ac force stabilizes the dynamics, allowing the generation of uniform directed motion over a range of momentum much larger than what is possible with a dc bias. We explain such a stabilization of the dynamics by observing that a nonadiabatic ac drive broadens the effective cooling momentum range and forces the atom trajectories to cover such a region. Thus the system can dissipate energy and maintain a steady-state energy balance. Our results show that in the case of a finite-range velocity-dependent friction, a ratchet device may offer the possibility of controlling the particle motion over a broader range of momentum with respect to a purely biased system, although this is at the cost of a reduced coherency.« less
  • We present a very simple model for realizing directed transport with cold atoms in a pair of periodically flashed optical lattices. The origin of this ratchet effect is explained and its robustness demonstrated under imperfections typical of cold atom experiments. We conclude that our model offers a clear-cut way to implement directed transport in an atom optical experiment.
  • We theoretically study the observable response of edge currents in two-dimensional cold atom optical lattices. As an example, we use Gutzwiller mean-field theory to relate persistent edge currents surrounding a Mott insulator in a slowly rotating trapped Bose-Hubbard system to time of flight measurements. We briefly discuss an application, the detection of the Chern number using edge currents of a topologically ordered optical lattice insulator.
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