Penetration depth study of LaOs4Sb12 : Multiband s-wave superconductivity

Authors: X. Y. Tee, H. G. Luo, T. Xiang, D. Vandervelde, M. B. Salamon, H. Sugawara, H. Sato, C. Panagopoulos, and Elbert E. M. Chia

Published in: Physical Review B 86, 064518 (2012), 2012.

We measured the magnetic penetration depth λ(T) in single crystals of LaOs4Sb12
(Tc = 0.74 K) down to 85 mK using a tunnel-diode-oscillator technique. The observed low-temperature exponential dependence indicates an s-wave gap.
Fitting the low-temperature data to a BCS s-wave expression gives the zero-temperature gap value (0) = (1.34 ± 0.07)kBTc which is significantly smaller than the BCS value of 1.76kBTc .
In addition, the normalized superfluid density ρ(T) shows an unusually long suppression near Tc and is best fit by a two-band s-wave model.