Heat Conduction in the Vortex State of NbSe_2: Evidence for Multi-Band Superconductivity

TL;DR

This study measures thermal conductivity in NbSe_2 to reveal evidence of multi-band superconductivity, showing distinct regimes of quasiparticle behavior linked to different superconducting gaps on separate Fermi surface sheets.

Contribution

It provides experimental evidence for multi-band superconductivity in NbSe_2 through thermal conductivity measurements in the vortex state.

Findings

Identification of localized and delocalized quasiparticle regimes

Distinct length scales corresponding to different superconducting gaps

Comparison with MgB_2 and V_3Si supports multi-band behavior

Abstract

The thermal conductivity kappa 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 naturally explained as multi-band superconductivity, with distinct small and large superconducting gaps on different sheets of the Fermi surface. This behavior is compared to that of the multi-band superconductor MgB_2 and the conventional superconductor V_3Si.