|M.Sc Student||Itah Amir|
|Subject||Ultra Cold Rubidium Atoms at Bose-Einstein Condensation|
Loaded into External Periodic Potential
|Department||Department of Physics||Supervisor||Professor Jeff Steinhauer|
|Full Thesis text|
Many-body boson-particles have a unique phase, known as the Bose Einstein Condensate (BEC). Below a critical temperature, the boson-particles undergo a phase transition into the BEC state. In 1995, the first BEC in dilute atomic gases was realized. The BEC in dilute atomic gases is an important tool for studying many- body physics, since a variety of parameters, including external potential, size, density, and interaction strength can be controlled.
My thesis concerns an experiment which studies the many-body physics of ultra-cold atomic gases. In my experiment, a Bose Einstein Condensate (BEC) is loaded into a two dimensional optical lattice. The lattice potential is formed by carrying out a Fourier Transform (FT) with a lens to four laser beams which obtained from a microlens array. In this study we observed that the distribution of atoms is not uniform. An accumulation of atoms was observed. This accumulation was not predicted. In addition, it was also observed that the number of atoms (which are trapped inside the periodic potential) decrease as a function of time.
The analysis of the results indicates that if we assume that the Gross-Pitaevskii Equation (GPE) describes our experiment then the phenomenon of Macroscopic
Quantum Self Trapping (MQST) can explain the accumulation of atoms which was observed in the results. In addition, MQST can also predict if an accumulation of atoms will occur. However, the results of 3D GPE numerical simulation did not predict the experimental observations. The simulation did not result in an accumulation of atoms. The simulation results led to doubts about the capabilities of the GPE to describe our experiment. Perhaps the theory is incomplete and needs to be expanded. If this is the case, then MQST cannot explain the phenomenon of the accumulation of atoms. Future research will be necessary to further investigate this phenomenon.