Abstract
The superconducting gap structure of LaFePO is studied by thermal conductivity at low temperatures in fields parallel and perpendicular to the axis. A clear two-step field dependence of with a characteristic field much lower than the upper critical field is observed. In spite of the large anisotropy of , in both directions is nearly identical below . Above , grows gradually with with a convex curvature, followed by a steep increase with strong upward curvature near . These results indicate multigap superconductivity with active two-dimensional (2D) and passive three-dimensional bands having contrasting gap values. Together with the recent penetration depth results, we suggest that the 2D bands consist of nodal and nodeless ones, consistent with extended -wave symmetry.
- Received 14 July 2009
DOI:https://doi.org/10.1103/PhysRevB.80.220509
©2009 American Physical Society