Ferro-deformation at the nuclear system with protons, Z = 20 and   neutrons, N = 40: 60Ca
  We present a possibility that the system with Z = 20, N = 40, 60Ca, has a large deformation, even though it has both proton and neutron magic numbers, symbolizing a spherical nucleus. This large deformation corresponds to the so-called ferro-deformation that occurs at the particular critical points over the nuclear chart. By comparisons with the ferra-deformation at the critical point Z = 40, N = 64 [arXiv:1604.02786], we draw a conclusion that shape phase transitions should occur at Z = 18 or 20 when N = 36 to 38, which leads to a ferro-deformation at the critical points of Z = 18 or 20, N = 40; 58Ar, 60Ca. We explain the shape phase transition in terms of isospin dependent spin-orbital interactions between neutrons in the f5/2 orbital and protons in the f7/2 orbital. We find a universal behavior over the nuclear chart for yielding the ferro-deformation such that; Z = 64, N = 104, Z = 40, N = 64, and Z = 20, N = 40, respectively. This feature is linked to concept of the neutron(n)-proton(p)interaction in spin-orbital couplings such that; nh9/2-ph11/2, ng7/2-pg9/2, and nf5/2-pf7/2, respectively. It is suggested that triple shape coexistence would be possible in the Z = 20, N = 36, 56Ca, and the Z = 18, N = 36, 54Ar, where the ferro-deformation is expected to be built on the second 0+ state. The predicted level schemes for 52Ar, 54Ar, 56Ar, 56Ca, 58Ca, and 60Ca are presented. 
Chang-Bum Moon
nucl-th nucl-ex