Experimental Determination of the Temperature-Dependent Penetration Depth in V sub 3 Si

摘要

Small angle neutron diffraction from the flux-line lattice (FLL) in a high quality, single crystal of superconducting V sub 3 Si has been used to deduce the low-field penetration depth lambda (T). An absolute determination is possible because the FLL form factor F/sub hk/ is essentially single-valued in the scattering vector magnitude absolute value of K/sub hk/, as well as nearly London-like at low field. We obtain lambda (0) = 102 +- 1 nm, 20% to 30% larger than previous determinations of the London penetration depth lambda/sub L/ (0). The temperature dependence of lambda (T) is found to deviate from that of the BCS theory. An assessment of the data indicates the most prominent source of the discrepancy is due to strong electron-phonon coupling, and we find 2 delta (0)/k/sub B/T/sub c/ = 3.88 +- 0.07, in reasonable agreement with values found in the literature. (ERA citation 09:043825)