Observation of a Hidden Hole-Like Band Approaching the Fermi Level in K-Doped Iron Selenide Superconductor

• Published in: arXiv.org 2016-06
• Main Authors: Sunagawa, Masanori, Terashima, Kensei, Hamada, Takahiro, Fujiwara, Hirokazu, Fukura, Tetsushi, Takeda, Aya, Tanaka, Masashi, Takeya, Hiroyuki, Takano, Yoshihiko, Arita, Masashi, Shimada, Kenya, Namatame, Hirofumi, Taniguchi, Masaki, Suzuki, Katsuhiro, Usui, Hidetomo, Kuroki, Kazuhiko, Wakita, Takanori, Muraoka, Yuji, Yokoya, Takayoshi
• Format: Article
• Language: English
• Subjects: Alkali metals; Arsenides; Electrons; Fermi surfaces; Iron; Nesting; Superconductivity
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1606.02405

One of the ultimate goals of the study of iron-based superconductors is to identify the common feature that produces the high critical temperature (Tc). In the early days, based on a weak-coupling viewpoint, the nesting between hole- and electron-like Fermi surfaces (FSs) leading to the so-called \(s\pm\) state was considered to be one such key feature. However, this theory has faced a serious challenge ever since the discovery of alkali-metal-doped FeSe (AFS) superconductors, in which only electron-like FSs with a nodeless superconducting gap are observed. Several theories have been proposed, but a consistent understanding is yet to be achieved. Here we show experimentally that a hole-like band exists in KxFe2-ySe2, which presumably forms a hole-like Fermi surface. The present study suggests that AFS can be categorized in the same group as iron arsenides with both hole- and electron-like FSs present. This result provides a foundation for a comprehensive understanding of the superconductivity in iron-based superconductors.