Quantum Accelerator Modes at higher order resonances

Quantum Accelerator Modes (QAM) are produced by subjecting cold atoms to standing wave pulses, when these pulses are applied in the direction of gravity. A group of atoms get accelerated. Normally, QAMs are seen whenever pulse period is choosen close to an integer multiple of a time called the half Talbot time. These times are referred to as primary resonance times [1]. We, using BEC, show for the first time that QAMs can be observed at rational fractions of Talbot time, called higher order resonance times. The details and the latest experimental data will be presented. [1] G. Behin-Aein, V. Ramareddy, P. Ahmadi, G. S. Summy, Phys. Rev. Lett. (accepted for publication), arXiv physics/0609203.