Mid Term Review

Metastable Helium BEC in an optical dipole potential and optical lattice simulation

Mr Abbas Hussein
Laser Physics Centre, ANU

Unlike alkali gases, He* BEC is realized in its metastable state 2³ S1 rather than the electronic ground state. Owing to the huge internal energy of 23 S1, nearly 20eV above the ground state, single atom detection with a high precision is possible. The ability of single-atom detection opens the path to explore many body phenomena on single atom basis. Quantum phase transition such as superfluid-Mott insulator phase transition, BEC-BCS crossover can be addressed with high resolution. We report the realisation of Bose-Einstein condensation (BEC) with metastable helium atoms using an in-vacuum coil magnetic trap and optical dipole trap. The entire experimental sequence takes under 4 seconds, with BECs observed with ~ 1 × 106 after evaporative cooling in the dipole trap. 

A theoretical study has been performed on 2D bipartite square lattice. Hybridisation of different orbital states hosted by this lattice enables investigation of novel orbital physics phenomena. In the pioneering work by Hemmerich et.al s-p-hybridized orbital states of the atomic condensate were observed in a checkerboard-like lattice. In this system, interaction between different orbital states can be observed. To this end, the band structure of our model and Bloch wave functions are constructed using the plane wave expansion method as well as the tight-binding approximation. Furthermore, using a coupled-mode theory for energy-degenerate states, we demonstrate the possibility to create superposition states with a nontrivial orbital texture.

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