Multi-band superconductivity in NbSe2 from heat transport

Abstract The thermal conductivity of the layered s-wave superconductor NbSe 2 was measured down to T c /100 throughout the vortex state. With increasing field, we identify two regimes: one with localized states at fields very near H c1 and one with highly delocalized quasiparticle excitations at higher fields. The two associated length scales are most naturally explained as multi-band superconductivity, with distinct small and large superconducting gaps on different sheets of the Fermi surface.