Related papers: Coherent ratchets in driven Bose-Einstein condensa…
We experimentally investigate the phenomenon of a quantum ratchet created by exposing a Bose-Einstein Condensate to short pulses of a potential which is periodic in both space and time. Such a ratchet is manifested by a directed current of…
The ratchet phenomenon is a means to get directed transport without net forces. Originally conceived to rectify stochastic motion and describe operational principles of biological motors, the ratchet effect can be used to achieve…
C. E. Creffield and F. Sols (Phys. Rev. Lett. 103, 200601 (2009)) recently reported finite, directed time-averaged ratchet current, for a noninteracting quantum particle in a periodic potential even when time-reversal symmetry holds. As we…
We study the crossover between classical and quantum dynamics by observing the behavior of a quantum ratchet created by exposing a Bose-Einstein condensate to short pulses of a potential which is periodic in both space and time. Such a…
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…
We demonstrate the operation of a quantum ratchet in the absence of dissipative processes within the observation time (Hamiltonian regime). An atomic rubidium Bose-Einstein condensate is exposed to a sawtooth-like optical lattice potential,…
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…
We study the behavior of a Bose-Einstein condensate held in an optical lattice. We first show how a self-trapping transition can be induced in the system by either increasing the number of atoms occupying a lattice site, or by raising the…
We study the rectification process of interacting quantum particles in a periodic potential exposed to the action of an external ac driving. The breaking of spatio-temporal symmetries leads to directed motion already in the absence of…
Quantum-resonance ratchets associated with the periodically kicked particle are experimentally realized for the first time. This is achieved by using a Bose-Einstein condensate exposed to a pulsed standing light wave and prepared in an…
We demonstrate that the combined effect of a spatially periodic potential, lateral confinement and spin-orbit interaction gives rise to a quantum ratchet mechanism for spin-polarized currents in two-dimensional coherent conductors. Upon…
We generate spin currents in an $^{87}$Rb spin-2 Bose-Einstein condensate by application of a magnetic field gradient. The spin current destroys the spin polarization, leading to a sudden onset of two-body collisions. In addition, the spin…
We propose a scheme for producing directed motion in a lattice system by applying a periodic driving potential. By controlling the dynamics by means of the effect known as coherent destruction of tunneling, we demonstrate a novel…
Quantum-resonance ratchets have been realized over the last ten years for the production of directed currents of atoms. These non-dissipative systems are based on the interaction of a Bose-Einstein condensate with an optical standing wave…
We study the noise-induced currents and reliability or coherence of transport in two different classes of rocking ratchets. For this, we consider the motion of Brownian particles in the over damped limit in both adiabatic and non-adiabatic…
Quantum ratchets exhibit asymptotic currents when driven by a time-periodic potential of zero mean if the proper spatio-temporal symmetries are broken. There has been recent debate on whether directed currents may arise for potentials which…
We study the effect of a strong, oscillating driving field on the dynamics of ultracold bosons held in an optical lattice. Modeling the system as a Bose-Hubbard model, we show how the driving field can be used to produce and maintain a…
A ring-shaped array of Bose-Einstein condensed atomic gases can display circular currents if the relative phase of neighboring condensates becomes locked to certain values. It is shown that, irrespective of the mechanism responsible for…
The interplay between disorder and interactions is a "leit-motiv" of condensed matter physics, since it constitutes the driving mechanism of the metal-insulator transition. Bose-Einstein condensates in optical potentials are proving to be…
We study quantum transport of an interacting Bose-Einstein condensate in a two-dimensional disorder potential. In the limit of vanishing atom-atom interaction, a sharp cone in the angle-resolved density of the scattered matter wave is…