title: S-wave spin-triplet order in superconductors without inversion symmetry: Li2Pd3B and Li2Pt3B.
abstract: We investigate the order parameter of noncentrosymmetric superconductors Li2Pd3B and Li2Pt3B via the behavior of the penetration depth lambda(T). The low-temperature penetration depth shows BCS-like behavior in Li2Pd3B, while in Li2Pt3B it follows a linear temperature dependence. We propose that broken inversion symmetry and the accompanying antisymmetric spin-orbit coupling, which admix spin-singlet and spin-triplet pairing, are responsible for this behavior. The triplet contribution is weak in Li2Pd3B, leading to a wholly open but anisotropic gap. The significantly larger spin-orbit coupling in Li2Pt3B allows the spin-triplet component to be larger in Li2Pt3B, producing line nodes in the energy gap as evidenced by the linear temperature dependence of lambda(T). The experimental data are in quantitative agreement with theory.
authors.affiliation: Department of Physics, University of Illinois at Urbana and Champaign, 1110 West Green Street, Urbana, Illinois 61801, USA. yuan@mrl.uiuc.edu
authors.forename: H Q
authors.initials: HQ
authors.lastname: Yuan
authors.forename: D F
authors.initials: DF
authors.lastname: Agterberg
authors.forename: N
authors.initials: N
authors.lastname: Hayashi
authors.forename: P
authors.initials: P
authors.lastname: Badica
authors.forename: D
authors.initials: D
authors.lastname: Vandervelde
authors.forename: K
authors.initials: K
authors.lastname: Togano
authors.forename: M
authors.initials: M
authors.lastname: Sigrist
authors.forename: M B
authors.initials: MB
authors.lastname: Salamon