title: Universal equation of state and pseudogap in the two-dimensional Fermi gas.
abstract: We determine the thermodynamic properties and the spectral function for a homogeneous two-dimensional Fermi gas in the normal state using the Luttinger-Ward, or self-consistent T-matrix, approach. The density equation of state deviates strongly from that of the ideal Fermi gas even for moderate interactions, and our calculations suggest that temperature has a pronounced effect on the pressure in the crossover from weak to strong coupling, consistent with recent experiments. We also compute the superfluid transition temperature for a finite system in the crossover region. There is a pronounced pseudogap regime above the transition temperature: the spectral function shows a Bogoliubov-like dispersion with backbending, and the density of states is significantly suppressed near the chemical potential. The contact density at low temperatures increases with interaction and compares well with both experiment and zero-temperature Monte Carlo results.
authors.affiliation: Cavendish Laboratory, Cambridge CB3 0HE, United Kingdom.
authors.forename: Marianne
authors.initials: M
authors.lastname: Bauer
authors.affiliation: London Centre for Nanotechnology, Gordon Street, London WC1H 0AH, United Kingdom.
authors.forename: Meera M
authors.initials: MM
authors.lastname: Parish
authors.affiliation: Institut für Theoretische Physik, Universität Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Tilman
authors.initials: T
authors.lastname: Enss