Making a spin-difference in quantum gases

Miikka Heikkinen

Research output: ThesisDoctoral ThesisCollection of Articles


This thesis studies the theory of quantum gases. We focus on fermionic superfluidity in systems in which the control over the spin degree of freedom has a central role. We explain the microscopic origin of the spin-asymmetric Josephon effect, and propose methods for realizing this effect experimentally in quantum gases. We investigate the phenomenon of fermionic superfluidity in the presence of spin-polarization, with our main focus on the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) phase. We show that the FFLO pairing mechanism leads to an anisotropic speed of sound which can be used to identify the state in experiments. Using real-space dynamical mean field theory (DMFT), we compute the phase diagram of a trapped, spin-polarized Fermi gas in a dimensional crossover from a 1D to a 3D optical lattice. We find that the FFLO state is realized in a broad region of parameters throughout the crossover while the shell structure of the Fermi gas preceding the transition to the full FFLO state shows a strong dependence on the dimensionality. Finally, we utilize the cluster DMFT method to show that the FFLO state is stable against non-local quantum fluctuations even though these fluctuations do affect the critical temperature of the state.
Translated title of the contributionSpin-asymmetria kvanttikaasuissa
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
  • Törmä, Päivi, Supervising Professor
  • Törmä, Päivi, Thesis Advisor
Print ISBNs978-952-60-5708-8
Electronic ISBNs978-952-60-5709-5
Publication statusPublished - 2014
MoE publication typeG5 Doctoral dissertation (article)


  • quantum gases
  • superfluidity
  • optical lattice
  • Hubbard model
  • Josephson effect
  • Fulde-Ferrell-Larkin-Ovchinnikov phase
  • generalized random-phase approximation
  • dynamical mean-field theory


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