Muon-spin-rotation measurements of the penetration depth in Li2Pd3B

Measurements of the magnetic field penetration depth lambda in the ternary boride superconductor Li2Pd3B (T-c similar or equal to 7.3 K) have been carried out by means of muon-spin rotation (mu SR). The absolute values of lambda, the Ginzburg-Landau parameter kappa, and the first H-c1 and second H-c2 critical fields at T=0 obtained from mu SR were found to be lambda(0)=252(2) nm, kappa(0)=27(1), mu H-0(c1)(0)=9.5(1) mT, and mu H-0(c2)(0)=3.66(8) T, respectively. The zero-temperature value of the superconducting gap Delta(0)=1.31(3) meV was found, corresponding to the ratio 2 Delta(0)/k(B)T(c)=4.0(1). At low temperatures lambda(T) saturates and becomes constant below T similar or equal to 0.2T(c), in agreement with what is expected for s-wave BCS superconductors. Our results suggest that Li2Pd3B is a s-wave BCS superconductor with only one isotropic energy gap.