Coexistence of superconductivity with quadrupole order in a system

Kubo, Katsunori 

Superconductivity in a model on a cubic lattice for a non-Kramers system is discussed. In our previous studies, we have found that -wave superconductivity with symmetry occurs in a wide parameter range in a system. In such an anisotropic superconducting state, the cubic symmetry of the system can be broken. Since the quadrupole degrees of freedom is active in a system, the effect of cubic symmetry breaking should be important. In or superconducting state, a ferroquadrupole moment of becomes finite. In this study, we investigate the coexisting states of the superconductivity and ferroquadrupole order of by a mean-field theory. Then, we find that superconducting transition temperature can be increased by the quadrupole ordering.