Abstract
We investigate both experimentally and theoretically disorder- induced damping of Bloch oscillations of Bose–Einstein condensates in optical lattices. The spatially inhomogeneous force responsible for the damping is realized by a combination of a disordered optical and a magnetic gradient potential. We show that the inhomogeneity of this force results in a broadening of the quasimomentum spectrum, which in turn causes damping of the centre-of-mass oscillation. We quantitatively compare the obtained damping rates to the simulations using the Gross–Pitaevskii equation. Our results are relevant for high precision experiments on very small forces, which require the observation of a large number of oscillation cycles.
Highlights
The acceleration of particles in periodic potentials leads to an oscillatory motion instead of a linear increase in velocity
We have presented the first experimental investigation on disorder-induced damping of Bloch oscillations of BECs
The observed damping rates are in good agreement with predictions based on numerical solutions of the full GPE and show that the underlying physical mechanism for the damping is the broadening of the quasimomentum spectrum due to the spatially varying phase evolution of the condensate
Summary
The acceleration of particles in periodic potentials leads to an oscillatory motion instead of a linear increase in velocity. Since this is a pure single particle effect, it is possible to describe the underlying physics in a 1D model, while a quantitative analysis of the effects of disorder and interactions requires a 3D description, as reported in a previous work [27]. It is necessary to reduce the dynamical instability in order to investigate the effect of the disorder on the Bloch oscillations This can be accomplished with a combination of a high potential gradient [31] and a reduction of the nonlinear interactions. In the experiments reported here the interactions were reduced by decreasing the density of the BEC, to enable the observations of disorder-induced damping of Bloch oscillations
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