Bright Solutions and dynamics in Bose-Fermi Mixtures

The study of wave mechanics and propagation in non-linear media is a fundamental concept within physics. In particular, solitons (non-dispersive wave packets) are a general solution to the non-linear wave equation. Their existence is maintained by a non-linear interaction that counteracts the effects of dispersion. We will investigate bright solitons in an ultracold quantum-degenerate Bose-Fermi mixture where the required non-linear interaction is provided by the attraction between the Bose and Fermi components. To date, although theoretically predicted, solitons have not been observed in a Bose-Fermi mixture. To achieve our goal, we will use a Bose-Einstein condensate of the bosonic isotope 87Rb and a spin-polarised degenerate Fermi gas of the fermionic isotope 40K. There is a vast wealth of theory regarding bright solitons in quantum degenerate matter, but only a few experimental realisations. As well as being of fundamental scientific interest, the realisation and characterisation of bright matter-wave solitons in a Bose-Fermi mixture could facilitate future experiments in such areas as soliton interferometry and soliton-surface interactions for the development of sensitive surface probes, which would, respectively, have ramifications for the fields of precision measurement and surface science. The experiment will be carried out using an atom chip, an experimental environment in which current carrying wires are used to create magnetic microtraps for the atoms. The atom chip has now become a standard tool for the easy, robust and fast production of Bose-Einstein condensates. In addition, the atom chip trap is an extremely good tool for studying quantum degenerate gases in a low-dimensional system (specifically an effectively 1D system), a proposed requirement for the realisation of bright solitons in Bose-Fermi mixtures. The main goals of the project are to ascertain experimentally under which conditions a Bose-Fermi mixture can be considered as one-dimensional, i.e., can be termed "effectively 1D"; the investigation of a new tool for varying atom-atom interaction strengths; the realisation of bright solitons in a Bose-Fermi mixture; the observation and characterisation of the formation and density profiles of single solitons and soliton trains; and, ultimately, the controlled collision of two bright matter-wave solitons.