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arXiv:cond-mat/0509602 · Physical Review Letters

Atomic Current across an Optical Lattice

Alexey V. Ponomarev, Javier Madroñero, Andrey R. Kolovsky, Andreas Buchleitner

Published Feb 9, 2006• 64 citations
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Abstract

We devise a microscopic model for the emergence of a collision-induced, fermionic atomic current across a tilted optical lattice. Tuning the--experimentally controllable--parameters of the microscopic dynamics allows us to switch from Ohmic to negative differential conductance.
DOI
10.1103/physrevlett.96.050404

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In the present thesis, we discuss the dynamical response to a static forcing of collisionally interacting, neutral fermionic atoms loaded into a one-dimensional optical lattice. It is well known that for a single particle, as well as for many non-interacting particles, there are two fundamental results: the Bloch oscillations of the total momentum and the absence of a net current, which are accompanied by the localization of the particles in configuration space. In our work, we recall (and, in the presence of an additional parabolic confinement, generalize) the single particle results and, then, solve the associated transport problem for two many-particle systems with non-vanishing atom-atom interactions. In the first case, we analyze the behavior of a two-component (i.e., non-pola-rized) fermionic gas under static forcing. We show that, while the atom-atom interactions do not induce a net current of fermions in this system, a variety of new phenomena emerge. These range from the amplitude modulation of Bloch oscillations with a new frequency, which is proportional to the interaction constant, over doubling of the Bloch frequency, to a rescaling of the characteristic time scales at strong interactions. In the second case, we discuss the requirements to witness directed atomic transport, and propose a microscopic model to describe the normal transport behavior of a dilute gas of polarized (hence non-interacting) fermions, where the net current emerges due to the collision-induced coupling with the finite bath, which is made of bosonic atoms loaded in to the same optical lattice. The outcome is a current-voltage'' characteristics which displays both Ohmic and negative differential conductivity, and a maximum current right at the transition between both regimes. This transition point is completely determined by the microscopic model parameters, and weakly depends on the bath temperature, while the current amplitude asymptotically vanishes with increasing temperature.