Superfluid equation of state of dilute composite bosons or how to include 3-and 4-body problems in the many body problem - Leyronas, X. and Combescot, R.
LASER PHYSICS 19, 599-601 (2009)
Abstract : We show how the 3 and 4-body problems emerge in the BEC limit of the
BEC-BCS crossover, where we treat explicitly dimers as made of two
fermions. We give the argument leading, at zero temperature, to the
calculation of the equation of state. We find that, when expanding the
chemical potential in powers of the density n up to the Lee-Huang-Yang
order, proportional to n (3/2), the result is identical to the one of
elementary bosons in terms of the dimer-dimer scattering length a (M) ,
the composite nature of the dimers appearing only in the next order term
proportional to n (2).