Ginzburg-Landau Formalism for 2n-Body Condensation

Abstract

The Ginzburg-Landau formalism is constructed for Fermi superfluidity based on the 2n-body condensation in parallel with the usual Ginzburg-Landau formalism for the Cooper pair condensation. By this formalism, the transition temperature of the 2n-body condensation is given compactly by the zero of coefficient of the quadratic term in the 2n-body condensed order parameter without counting complicated Feynman diagrams for the 2n-body condensation susceptibility. It is shown that the 2n-body condensed state is stabilized in the intermediate- or strong-coupling regime against the BCS state based on the Cooper pair condensation. This theory is applied to the case of the possible superfluid state of cold atomic gases such as $^9$Be and $^{173}$Yb; the quartet state is possible in the former case, while the sextet state is expected in the latter case. It is predicted that the $^{173}$Yb atomic gas so far attained satisfies the condition for the sextet condensed state to be realized.