第1回 物理工学科教室談話会 (講師:Prof. Qimiao Si)

平成21年度 第1回 物理工学科教室談話会

日 時: 平成21年5月20日(水)16:00-17:00
場 所: 工6号館 1階 大会議室
講演者: Prof. Qimiao Si (Rice University)
題 目: Electronic Correlations and Magnetic Frustration in the Iron Pnictides

Since the surprising discovery of high Tc superconductivity in the iron pnictides in 2008, a large body of physical properties have already been accumulated. These properties serve as a basis for considerations on the microscopic physics of these materials. Based on the fact that they are “bad metals”, I will make the case that these metallic systems are close to a Mott transition [1,2,3]. The corresponding incoherent electronic excitations are modeled in terms of localized magnetic moments, with J1-J2 superexchange interactions on the iron square lattice [1,2]; the resulting magnetic order, structural distortion, and spin-wave-like excitations are consistent with experiments. The coupling of the local moments to the coherent electronic excitations tunes the strength of antiferromagnetic order, leading to a magnetic quantum critical point [2,3]; emerging evidence for the latter will be summarized. The implications of these considerations for superconductivity will be discussed.

[1] Q. Si and E. Abrahams, PRL 101, 076401 (2008);
[2] J. Dai et al, PNAS 106, 4118 (2009);
[3] Q. Si et al, NJP 11, 045001 (2009)