Muon-spin rotation measurements of the penetration depth of the Mo3Sb7 superconductor

Measurements of the magnetic-field penetration depth lambda in superconductor Mo3Sb7 (T-c similar or equal to 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 H-c1 and the second H-c2 critical fields at T=0 are lambda(0)=720(100) nm, kappa(0)=55(10), mu H-0(c1)(0)=1.8(3) mT, and mu H-0(c2)(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 2 Delta(0)/k(B)T(c)=3.83(10). At low temperatures lambda(-2)(T) saturates and becomes constant below T similar or equal to 0.3T(c), 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.