Superconducting gap structure of heavy-Fermion compound URu2Si2determined by angle-resolved thermal conductivity

In heavy-Fermion compound URu 2 Si 2 , unusual superconductivity is embedded in an enigmatic 'hidden order' phase. Recently, it has been shown that URu 2 Si 2 is essentially a multiband superconductor associated with the semimetallic compensated electronic structure. Here, to pin down the detailed superconducting gap structure, we have performed thermal transport measurements on ultraclean URu 2 Si 2 single crystals in magnetic fields rotating various directions relative to the crystal axes. By changing the amplitude of magnetic fields, we determined the nodal topology of electron and hole band separately. The results indicate a new type of unconventional superconductivity with two distinct gaps, in which horizontal line nodes lie within the basal ab plane of the light-hole band with small gap and point nodes along the c -axis in the heavy electron band with large gap. This gap structure is consistent with 'chiral' d-wave symmetry with a form .