Magnetic penetration depth in layered compound NbSe2 measured by muon spin relaxation

Muon spin relaxation measurements in the layered superconductor NbSe2 have been performed to study the magnetic field penetration depth λ. The relaxation rate σ(T) α λ(T)−2 in field-cooled measurements exhibits a temperature dependence consistent with an isotropic energy gap without anomalous zeros. The low temperature penetration depth λ(T → 0) = 2,500 Å is much larger than that obtained from previous Hc1 measurements.