HiSORセミナー
The electronic structure of FeSe in the nematic phase
日時 2016年11月14日 （月） 15：00～16：00
場所 放射光科学研究センター 2階 セミナー室
講師 M. D. Watson
(Diamond Light Source)
FeSe is structurally the simplest of Fe-based superconductors, but its complex and unique properties pose important questions. In particular it exhibits a structural transition at 90 K which breaks the fourfold symmetry of the lattice, but unusually no magnetic ordering occurs at any temperature. This so-called “nematic” phase is a crucial feature of the phase diagram of Fe-based superconductors, but is not very well understood. However the availability of high-quality single crystals in recent years has enabled very detailed study of the electronic structure of FeSe, providing important insights on the origin and nature of the nematic phase.
In this talk I will discuss experimental determinations of the electronic structure of FeSe from magnetotransport, quantum oscillations and ARPES. The normal phase of FeSe is found to be a moderately correlated quasi-2D compensated metal, with much smaller Fermi surface pockets than the predictions of DFT. At low temperatures the Fermi surface is found to consist of one elliptical hole pocket, significantly distorted from the circular pocket observed at high temperature. The structure of the electron pockets at the M point of the Brillouin zone is a topic of current debate, but I will show that new ARPES data requires a revision of the previous understanding and leads to the requirement for a new order parameter to describe the nematic transition. Finally I will discuss ARPES measurements of the FeSe1-xSx series.
問合せ先 島田賢也（放射光科学研究センター）
