Optimization of unconventional superconductivity through Fermi surface topology

2015 Fiscal Year Final Research Report

• Project/Area Number: 24340079
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Osaka University
• Principal Investigator: Kuroki Kazuhiko 大阪大学, 理学(系)研究科(研究院), 教授 (10242091)
• Co-Investigator(Kenkyū-buntansha): MACHIDA Masahiko 独立行政法人日本原子力研究開発機構, システム計算科学センター, 研究主幹 (60360434) ; NAGAI Yuki 独立行政法人日本原子力研究開発機構, システム計算科学センター, 研究員 (20587026)
• Project Period (FY): 2012-04-01 – 2016-03-31
• Keywords: フェルミ面トポロジー / スピン揺らぎ / 鉄系超伝導 / バンド構造

Outline of Final Research Achievements

In the iron-based superconductors,　the　second　neighbor　hopping　can　dominate　over　the　nearest　one.　It is found that the s+-　superconductivity, which is a second neighbor pairing state, can be enhanced even when the Fermi surface nesting is partially degraded. This explains why superconductivity is even enhanced when large amount of electrons are doped in the hydrogen doped 1111 iron-based superconductors. The comparison with the cuprates is interesting in this context. In the cuprates, the nearest neighbor hopping always dominates, and hence d-wave pairing, a nearest neighbor pairing state, is most favorable. In both of these high Tc families, there is a good matching between real space and momentum space. Namely, when these real space pairing states are Fourier transformed, the obtained gap functions in momentum space have large amplitude on places where the density of states is large. This gives a general guiding principle of enhancing superconductivity.

Free Research Field

物性理論