Multiband superconductivity in NbSe_2 from heat transport

TL;DR

This study investigates heat transport in NbSe_2, revealing evidence of multiband superconductivity through distinct quasiparticle behaviors and gap structures across different Fermi surface sheets.

Contribution

The paper provides experimental evidence for multiband superconductivity in NbSe_2 by analyzing heat transport and quasiparticle localization at various magnetic fields.

Findings

Identification of localized states near H_c1

Observation of delocalized quasiparticles at higher fields

Evidence of multiple superconducting gaps on different Fermi surface sheets

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.