Expansion dynamics in fermionic quantum gases

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Perustieteiden korkeakoulu | Doctoral thesis (article-based)
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Verkkokirja ( KB, 81 s.)
Aalto University publication series DOCTORAL DISSERTATIONS , 120/2011
In this work we study dynamics of fermionic quantum gases. Radio frequency spectroscopy, Josephson oscillations, and time-of-flight dynamics are studied theoretically, and with the help of numerical simulations using the time-evolving block decimation algorithm. The simulations of radio frequency spectroscopy shed light on the nature of excitations in a fermionic superfluid confined in a lattice. The Josephson oscillations in the presence of different potentials for up and down spins show that the asymmetric Josephson effect cannot be described by the traditionally established view of coherent tunnelling of Cooper pairs. The expansion dynamics of a band-insulating state reveals that we can explain the time development of two-component systems in a lattice using a simple two-site model. Finally, the time-of-flight expansion of an imbalanced superfluid restricted to move in one dimension provides a remarkably simple way for detecting the long-sought-for Fulde-Ferrell-Larkin-Ovchinnikov superfluid state.
Supervising professor
Törmä, Päivi, Prof.
Thesis advisor
Törmä, Päivi, Prof.
Fermi gas, superfluidity, Fermi-Hubbard, TEBD, Kadanoff-Baym, superconductivity, cold gases, the Josephson effect, unitary dynamics, FFLO, collision dynamics
Other note
  • [Publication 1]: M.J. Leskinen, V. Apaja, J. Kajala, and P. Törmä, Quasiparticles, coherence and nonlinearity: exact simulations of RF-spectroscopy of strongly interacting one-dimensional Fermi gases, Physical Review A 78, 023602, August 2008. © 2008 American Physical Society (APS). By permission.
  • [Publication 2]: M.O.J. Heikkinen, F. Massel, J. Kajala, M.J. Leskinen, G.S. Paraoanu, and P. Törmä, Spin-asymmetric Josephson effect, Physical Review Letters 105, 225301, November 2010. © 2010 American Physical Society (APS). By permission.
  • [Publication 3]: J. Kajala, F. Massel, and P. Törmä, Expansion dynamics in the one-dimensional Fermi-Hubbard model, Physical Review Letters 106, 206401, May 2011. © 2011 American Physical Society (APS). By permission.
  • D, Advance online publication
    DOI: 10.1140/epjd/e2011-20081-8, 8 View at publisher
  • [Publication 5]: J. Kajala, F. Massel, and P. Törmä, Expansion dynamics of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, Physical Review A 84, 041601(R), October 2011. © 2011 American Physical Society (APS). By permission.