Evidence for a nodal-line superconducting state in LaFePO.
In several iron-arsenide superconductors there is strong evidence for a fully gapped superconducting state consistent with either a conventional s-wave symmetry or an unusual s{+/-} state where the gap changes sign between the electron and hole Fermi-surface sheets. Here we report measurements of the penetration depth lambda(T) in very clean samples of the related iron-phosphide superconductor, LaFePO, at temperatures down to approximately 100 mK. We find that lambda(T) varies approximately linearly with T strongly suggesting the presence of gap nodes in this compound. Taken together with other data, this suggests the gap function is not universal for all pnictide superconductors.
Fletcher
J D
JD
H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, BS8 1TL, United Kingdom.
Serafin
A
A
Malone
L
L
Analytis
J G
JG
Chu
J-H
JH
Erickson
A S
AS
Fisher
I R
IR
Carrington
A
A