Abstract

Measurements of the magnetic-field penetration depth lambda in superconductor Mo3Sb7 (Tc~=2.1 K) were carried out by means of muon-spin rotation. The absolute values of lambda, the Ginzburg-Landau parameter kappa, and the first Hc1 and the second Hc2 critical fields at T=0 are lambda(0)=720(100) nm, kappa(0)=55(10), µ0Hc1(0)=1.8(3) mT, and µ0Hc2(0)=1.9(2) T. The zero-temperature value of the superconducting energy gap Delta(0) was found to be 0.35(1) meV, corresponding to the ratio 2Delta(0)/kBTc=3.83(10). At low temperatures lambda−2(T) saturates and becomes constant below T~=0.3Tc, in agreement with what is expected for s-wave BCS superconductors. Our results suggest that Mo3Sb7 is a superconductor with the single isotropic energy gap.