Eur. Phys. J. D 47, 421-425 (2008)
https://doi.org/10.1140/epjd/e2008-00060-0

Effect of the lattice alignment on Bloch oscillations of a Bose-Einstein condensate in a square optical lattice

¹ Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany
² Kirensky Institute of Physics, 660036 Krasnoyarsk, Russia
³ Siberian Federal University, 660041 Krasnoyarsk, Russia

Corresponding author: ^a mccchung@pks.mpg.de

Received: 5 November 2007
Revised: 26 February 2008
Published online: 4 April 2008

Abstract

We consider a Bose-Einstein condensate of ultracold atoms loaded into a square optical lattice and subject to a static force. For vanishing atom-atom interactions the atoms perform periodic Bloch oscillations for arbitrary direction of the force. We study stability of these oscillations for non-vanishing interactions, which is shown to depend on an alignment of the force vector with respect to the lattice crystallographic axes. If the force is aligned along any of the axes, the mean field approach can be used to identify the stability conditions. On the contrary, for a misaligned force one has to employ the microscopic approach, which predicts periodic modulation of Bloch oscillations in the limit of a large forcing.