We propose a minimum single-band model for the newly discovered iron-based superconducting KxFe2Se2. Our model is found to be numerically consistent with the five-orbital model at low energies. Based on our model and the random phase approximation, we study the spin fluctuation and the pairing symmetry of superconducting gap function. The (π/2,π/2) spin excitation and the dx2−y2 pairing symmetry are revealed. All of the results can well be understood in terms of the interplay between the Fermi surface topology and the local spin interaction, providing a sound picture to explain why the superconducting transition temperature is as high as to be comparable to those in pnictides and some cuprates. A common origin of superconductivity is elucidated for this compound and other high-Tc materials.
@article{arxiv.1108.3491,
title = {A minimum single-band model for low-energy excitations in superconducting K$_x$Fe$_2$Se$_2$},
author = {Tao Zhou and Z. D. Wang},
journal= {arXiv preprint arXiv:1108.3491},
year = {2015}
}