Abstract
We report specific-heat measurements on well characterized single crystals of the Fe-based superconductor , from the same batch on which previous penetration depth, NMR, and thermal-conductivity measurements have observed a high density of low-energy excitations, which have been interpreted in terms of order-parameter nodes. Within the resolution of our measurements, the low-temperature limiting is found to be linear in field, i.e., we find no evidence for a Volovik effect associated with nodal quasiparticles in either the clean or dirty limit. We discuss possible reasons for this apparent contradiction, which may be an intrinsic feature of the multiple Fermi-surface sheets present in the iron pnictide superconductors.
- Received 15 February 2010
DOI:https://doi.org/10.1103/PhysRevB.81.214507
©2010 American Physical Society