Volume 85, Number 5, March 2009
Article Number 57007
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 20 March 2009
EPL, 85 (2009) 57007
DOI: 10.1209/0295-5075/85/57007

Pairing symmetry and properties of iron-based high-temperature superconductors

Yuan Wan and Qiang-Hua Wang

National Laboratory of Solid State Microstructures & Department of Physics, Nanjing University Nanjing 210093, China

received 15 January 2009; accepted in final form 19 February 2009; published March 2009
published online 20 March 2009

Pairing symmetry is important to indentify the pairing mechanism. The analysis becomes particularly timely and important for the newly discovered iron-based multi-orbital superconductors. From the group theory point of view we classified all pairing matrices (in the orbital space) that carry irreducible representations of the system. The quasiparticle gap falls into three categories: full, nodal and gapless. The nodal-gap states show conventional Volovik effect even for on-site pairing. The gapless states are odd in the orbital space, have a negative superfluid density and are therefore unstable. In connection to experiments we proposed possible pairing states and implications for the pairing mechanism.

74.20.-z - Theories and models of superconducting state.
74.20.Rp - Pairing symmetries (other than s-wave).
74.25.Jb - Electronic structure.

© EPLA 2009