Avalanches in Bose-Einstein Condensates
Since Bose-Einstein condensates (BECs) became an experimental reality, much effort is made to characterize its properties. A very attractive field is the study of the dynamics of ultra cold atoms in optical lattices with its potential application in quantum computation and the emerging atomtronics technologies. We investigate the atom current emitted from a BEC, where the BEC is loaded into a leaky optical lattice. In ref. [1] the open Bose-Hubbard model with two sites was analyzed. Here, we present results on the nonlinear mean field dynamics in larger 1D lattices with a coupling to the outside at both ends, which can be realized experimentally, e.g., by gravitation or by applying additional microwave fields.
We find [2] that for some critical values of the interatomic interaction strength, the current decays in avalanches that follow a power-law distribution (see Fig. 1) and indicate the existence of a novel phase transition. This behavior is due to the creation of discrete breathers. We show that the power law distribution of avalanches of BECs leaving the optical trap reflects the complexity and the hierarchical structure of the underlying classical mixed phase space.
Figure 1: Distribution (over initial conditions) of avalanches P(δP) for an open optical lattice with a rescaled interatomic interaction U/M=2, where M=128 is the sample size, and U is the interatomic interactions (in units of the intra-tunneling rate). A scale free power law distribution is evident. The best linear fit is indicated with the red dashed line. Inset: A representative realization of the decaying BEC population P(t) showing avalanches.
References
[1] M. Hiller, T. Kottos, and A. Ossipov, Phys. Rev. A 73, 063625 (2006)
Members working within this Project:
Theo GeiselRagnar Fleischmann
Former Members:
Holger HennigTsampikos Kottos
Moritz Hiller
