Quantum phase crossover in the spherical mean-field plus quadrupole–quadrupole and pairing model with two j-orbits

Abstract

The shape phase crossover in the mean-field plus the geometric quadrupole–quadrupole and pairing model within two [Formula: see text]-orbits is analyzed, for which a simple description of [Formula: see text]Sn confined in the lowest [Formula: see text] and [Formula: see text] orbits above the [Formula: see text]Sn core is demonstrated to reveal the crossover behavior of the model. It is shown that [Formula: see text], [Formula: see text] and [Formula: see text], [Formula: see text] in this case may serve as effective order parameters for even–even and odd-A systems, respectively, from which the shape phase crossover from the rotation-like phase to the superconducting-like phase can be observed with variation of the number of valence neutrons.