セミナー案内

日時
    
4月19日 (水), 13:30-
場所
京都大学理学部 5号館 413
講演者
Dr. Jun Ishizuka
(Condensed Matter Theory Group)
タイトル
"Spin and orbital fluctuations and pairing mechanisms of iron-based superconductors"
備考欄 (アブストラクト等)

Abstract:
Iron-based superconductors have been extensively studied as a complex multi-orbital system. Despite numerous efforts, the origin of pairing mechanism remains unknown.
Recently, angular resolved photoemission spectroscopy and quantum oscillation measurements [1] on FeSe reveal that the hole-pocket around G-point is pushed downward under the Fermi energy. To address this issue, we investigate the electronic state, the spin and orbital fluctuations, and the superconductivity in 16-band d-p model within the dynamical mean-field theory. We find that the dissipation of a shallow hole-pocket occurs by the orbital-dependent Coulomb interaction, which is corresponding to the recent experiment [1]. Furthermore, inter-site Coulomb interaction between iron d orbitals and selenium p orbitals drives an orbital order in absence of the low-energy spin response. We examine the superconducting gap structure in the orbital ordered phase by using the linearized Eliashberg equation, and find that the nodal-like s_±-wave pairing is realizedowing to the d_{yz} orbital component of the spin fluctuation.
We also discuss the pressure-temperature phase diagram of FeSe.


Reference:
[1] M. D. Watson et al., PRB 91, 155106 (2015).