Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1819123 | Physica C: Superconductivity and its Applications | 2009 | 7 Pages |
Abstract
We discuss the novel superconducting characteristics and unusual normal-state properties of iron (Fe)-based pnictide superconductors REFeAsO1ây (RE = La, Pr, Nd) and Ba0.6K0.4Fe2As2 (Tc = 38 K) by means of 57FeNMR and 75AsNQR/NMR. In the superconducting state of LaFeAsO0.7 (Tc = 28 K), the spin component of the 57Fe-Knight shift decreases to almost zero at low temperatures, which provide firm evidence of the superconducting state formed by spin-singlet Cooper pairing. The nuclear spin-lattice relaxation rates (1/T1) in LaFeAsO0.7 and Ba0.6K0.4Fe2As2 exhibit a T3-like dependence without a coherence peak just below Tc, indicating that an unconventional superconducting state is commonly realized in these Fe-based pnictide compounds. All these events below Tc are consistently argued in terms of an extended s±-wave pairing with a sign reversal of the order parameter among Fermi surfaces. In the normal state, 1/T1T decreases remarkably upon cooling for both the Fe and As sites of LaFeAsO0.7. In contrast, it gradually increases upon cooling in Ba0.6K0.4Fe2As2. Despite the similarity between the superconducting properties of these compounds, a crucial difference was observed in their normal-state properties depending on whether electrons or holes are doped into the FeAs layers. These results may provide some hint to address a possible mechanism of Fe-based pnictide superconductors.
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Condensed Matter Physics
Authors
H. Mukuda, N. Terasaki, M. Yashima, H. Nishimura, Y. Kitaoka, A. Iyo,