Thermodynamics of a n-p condensate in asymmetric nuclear matter

We study the neutron-proton pairing in nuclear matter as a function of isospin asymmetry at finite temperatures and the empirical saturation density using realistic nuclear forces and Brueckner-renormalized single particle spectra. Our computation of the thermodynamic quantities shows that, while the difference of the entropies of the superconducting and normal phases anomalously changes its sign as a function of temperature for arbitrary asymmetry, the grand canonical potential does not; the superconducting state is found to be stable in the whole temperature-asymmetry plane. The pairing gap completely disappears for density asymmetries exceeding alpha(c) = (rho(n)-rho(p))/rho approximately 0.11.