Studies on unusual normal state properties and spin/orbital physics in iron-based superconductors

2015 Fiscal Year Final Research Report

• Project/Area Number: 24684026
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Partial Multi-year Fund
• Research Field: Condensed matter physics II
• Research Institution: Kyoto University
• Principal Investigator: KASAHARA SHIGERU 京都大学, 理学(系)研究科(研究院), 助教 (10425556)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 鉄系超伝導 / 量子臨界点 / 電子ネマティック状態 / 擬ギャップ / 多軌道自由度 / 超シャロウバンド / BCS-BECクロスオーバー / 新奇超伝導状態

Outline of Final Research Achievements

In iron-based superconductors, spin and orbital degrees of freedom play an important role. An important task in the community is thus to uncover the unusual normal state properties related to the spin/orbital degrees of freedom. In this work, we have focused on the studies of quantum critical point (QCP) hidden beneath the superconducting dome as well as the electronic nematic transition above there. Our studies based on clean single crystals of BaFe2(As1-xPx)2 show the first evidence for the QCP beneath the superconducting dome, as well as the nematic transition in the normal state. These findings provide important clues for the understanding of iron-based superconductors. In the last year of this project, we have also investigated anomalous electronic properties and quantum condensate in iron-chalchogenides. In newly developed single crystals of FeSe, a cross-over from weakly coupled BCS state to tightly bound BEC state, as well as a possible new high-field phase have been found.

Free Research Field

固体電子物性