One dimensional transport of ultracold bosons

Simpson, David Peter (2014). One dimensional transport of ultracold bosons. University of Birmingham. Ph.D.

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Abstract

This thesis concerns the transport of ultracold bosons in a one-dimensional geometry. I consider two three-dimensional reservoirs of Bose-Einstein condensed atoms that are connected via weak tunnel junctions to each end of a one-dimensional channel. The particle current along the channel is driven only by a constant phase difference between the two reservoirs. I theoretically investigate the bosonic flow and develop a non-perturbative mean field description, showing the existence of metastable solutions for all values of tunnelling. I show there are two separate branches of the mean field solution and the lowest energy solution necessarily jumps discontinuously between these branches. I then demonstrate that such a mean field solution is robust against fluctuations for values of the Luttinger parameter pertinent to bosonic atoms and that fluctuations do not connect different branches of the mean field solution. I provide a possible experimental realisation utilising the versatility of atom chips and describe how one can experimentally observe both the phase profile in the channel and the particle flow along the channel. Finally, I explore the non-equilibrium dynamics following a quench in the tunnelling energy and demonstrate that such a quench can lead to switching between different branches of the mean field solution.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):