Exotic Superconducting Properties in the Electron-Hole-Compensated Heavy-Fermion 'Semimetal' URu_2Si_2

摘要

We show that the charge and thermal transport measurements on ultraclean crystals of URu_2Si_2 reveal a number of unprecedented superconducting properties. The uniqueness is best highlighted by the peculiar field dependence of thermal conductivity including the first-order transition at H_(c2) with a reduction of entropy flow. This is a consequence of multiband superconductivity with compensated electronic structure in the hidden order state of this system. We provide strong evidence for a new type of unconventional superconductivity with two distinct gaps having different nodal topology.