时 间: 2011年7月29日（周五）下午3:00

地 点: 清华大学高等研究院 科学馆322报告厅

题 目: Pairing Symmetry, Magnetism, and Mott Transition of K_yFe_xSe_2

报 告 人: Dr. Rong Yu

Department of Physics, Rice University

报告摘要: The discovery of superconductivity with a Tc ~ 30K in the new 122 iron-chalcogenides K_yFe_xSe_2, in the vicinity of an antiferromagnetically ordered and insulating state, promises to shed new light on both the role of electronic correlations and nature of magnetism and superconductivity of iron-based superconductors.By studying a multi-orbital Hubbard model using slave-rotor method, we show the band narrowing effects due to vacancy ordering may drive the system to a Mott insulating phase. By studying an extensive J1-J2 model, we further show vacancy ordering may also affects the exchange couplings in the insulating phase and results in exotic antiferromagnetic states.To understand the superconductivity in the 122 iron-chalcogenides, we study a multi-orbital t-J1-J2 model, and show that an A_1g s_{x^2y^2} state and a B_1g d_{x^2-y^2} state are quasi-degenerate in the J1~J2 magnetic frustration regime. We find the pairing amplitudes are of the same order as their pnictides counterparts, making it natural that the maximum Tc is comparable in the two systems.

References:

[1] R. Yu, J.-X. Zhu, and Q. Si, arXiv:1101.3307.

[2] R. Yu, P. Goswami, Q. Si, P. Nikolic, and J.-X. Zhu, arXiv:1103.3259.

[3] R. Yu, P. Goswami, and Q. Si, arXiv:1104.1445.