Multiple superconducting phases in heavy fermion compounds PrOs_4Sb_(12) and CeCoIn_5

摘要

In recently discovered heavy fermion compounds, quasi-two-dimensional CeCoIn_5 and skutterudite PrOs_4Sb_(12), multiple superconducting phases with different symmetries manifest themselves below T_c. The angle-resolved magnetothermal transport measurements revealed that in PrOs_4Sb_(12) a novel change in the symmetry of the superconducting gap function occurs deep inside the superconducting state. The ultrasound velocity measurements revealed that in CeCoIn_5 the Pulde-Ferrel-Larkin-Ovchinikov (FFLO) phase, in which the order parameter is spatially modulated and has planar nodes aligned perpendicular to the vortices, appears at low temperature and high field. These results open up a new realm for the study of the superconductivity with multiple phases.