arXiv subjects

Dario Poletti

Publications and source records attributed to Dario Poletti.

114 records · Page 7Linked to original sources

arXiv2009

Steering Bose-Einstein condensates despite time symmetry

A Bose-Einstein condensate in an oscillating spatially asymmetric potential is shown to exhibit a directed current for unbiased initial conditions despite time symmetry. This phenomenon occurs only if the interaction between atoms, treated in mean-field approximation, exceeds a critical value. Our findings can be described with a three-mode model (TMM). These TMM results corroborate well with a many-body study over a time scale which increases with increasing atom number. The duration of this time scale probes the validity of the used mean-field approximation.

physics.atom-ph↗

arXiv2008

Dynamics of matter-wave solitons in a ratchet potential

We study the dynamics of bright solitons formed in a Bose-Einstein condensate with attractive atomic interactions perturbed by a weak bichromatic optical lattice potential. The lattice depth is a biperiodic function of time with a zero mean, which realises a flashing ratchet for matter-wave solitons. The average velocity of a soliton and the directed soliton current induced by the ratchet depend on the number of atoms in the soliton. We employ this feature to study collisions between ratchet-driven solitons and find that soliton transport can be induced through their interactions. In the regime when matter-wave solitons are narrow compared to the lattice period the ratchet dynamics is well described by the effective Hamiltonian theory.

cond-mat.other↗

arXiv2007

Dissipationless Directed Transport in Rocked Single-Band Quantum Dynamics

Using matter waves that are trapped in a deep optical lattice, dissipationless directed transport is demonstrated to occur if the single-band quantum dynamics is periodically tilted on one half of the lattice by a monochromatic field. Most importantly, the directed transport can exist for almost all system parameters, even after averaged over a broad range of single-band initial states. The directed transport is theoretically explained within ac-scattering theory. Total reflection phenomena associated with the matter waves travelling from a tilting-free region to a tilted region are emphasized. The results are of relevance to ultracold physics and solid-state physics, and may lead to powerful means of selective, coherent, and directed transport of cold particles in optical lattices.

cond-mat.other↗

arXiv2006

Current behavior of a quantum Hamiltonian ratchet in resonance

We investigate the ratchet current that appears in a kicked Hamiltonian system when the period of the kicks corresponds to the regime of quantum resonance. In the classical analogue, a spatial-temporal symmetry should be broken to obtain a net directed current. It was recently discovered that in quantum resonance the temporal symmetry can be kept, and we prove that breaking the spatial symmetry is a necessary condition to find this effect. Moreover, we show numerically and analytically how the direction of the motion is dramatically influenced by the strength of the kicking potential and the value of the period. By increasing the strength of the interaction this direction changes periodically, providing us with a non-expected source of current reversals in this quantum model. These reversals depend on the kicking period also, though this behavior is theoretically more difficult to analyze. Finally, we generalize the discussion to the case of a non-uniform initial condition.

quant-ph↗

arXiv2006

Many-body quantum ratchet in a Bose-Einstein condensate

We study the dynamics of a dilute Bose-Einstein condensate confined in a toroidal trap and exposed to a pair of periodically flashed optical lattices. We first prove that in the noninteracting case this system can present a quantum symmetry which forbids the ratchet effect classically expected. We then show how many-body atom-atom interactions, treated within the mean-field approximation, can break this quantum symmetry, thus generating directed transport.

cond-mat.other↗

arXiv2006

Quantum resonance and anti-resonance for a periodically kicked Bose-Einstein Condensate in a one dimensional Box

We investigate the quantum dynamics of a periodically kicked Bose-Einstein Condensate confined in a one dimensional (1D) Box both numerically and theoretically, emphasizing on the phenomena of quantum resonance and anti-resonance. The quantum resonant behavior of BEC is different from the single particle case but the anti-resonance condition ($T = 2π$ and $α= 0$) is not affected by the atomic interaction. For the anti-resonance case, the nonlinearity (atom interaction) causes the transition between oscillation and quantum beating. For the quantum resonance case, because of the coherence of BEC, the energy increase is oscillating and the rate is dramatically affected by the many-body interaction. We also discuss the relation between the quantum resonant behavior and the KAM or non-KAM property of the corresponding classical system.

cond-mat.mes-hall↗