FeSe超导体的配对对称性，向列性和磁性研究

The discovery of iron-based superconductors in 2008 has attracted great attention, because these new superconductors could help to unlock secrets of high temperature superconductivity. Despite around 10 years intensive research, there remains problems unsolved such as the relationship among magnetism, nematicity and superconductivity, and the microscopic origin of the spin resonance peak observed in inelastic neutron scattering in the superconducting state. Here, we propose to study FeSe. FeSe is the structurally simplest iron-based superconductor, thus the fully understanding of the physics in FeSe could play a significant role on unravelling the mechanism of iron-based superconductors. Neutron scattering will be used to study the effect of pressure and chemical substitution on the crystal structure, nematicity, magnetic structure, and spin dynamics in FeSe, illustrating the coupling among magnetism, nematicity and superconductivity. Moreover, we propose to study the microscopic origin of spin resonance peak and its relationship to the pairing symmetry in this system.

2008年以来，铁基超导体的发现吸引了科学家们的广泛关注，因为它可能是解决高温超导机理的新途径。经过近10年的努力，虽然人们对铁基超导体的研究取得了很多进展，但是包括磁性、向列相和超导电性三者之间的关系，以及自旋共振峰的微观起源在内的关键问题仍然等待进一步的理解。在这样的背景下，FeSe吸引了科学家们的目光。作为结构最简单的高温超导体，FeSe是理解铁基超导机理和向列相机理的理想体系。在本项目中，我们将利用中子散射技术对FeSe超导体晶格结构、向列性、磁结构、自旋动力学行为随压力及化学掺杂的演变及它们与超导电性之间的耦合进行系统的研究，期望理解铁基超导和向列相的形成机理。同时用极化中子和外加磁场的方法来研究FeSe和掺杂FeSe中自旋共振峰的起源以及它们和超导配对对称性的关系。

FeSe和相关的铁基材料是理解铁基超导机理的关键体系。在本项目的支持下，研究团队在这个方向的代表性研究成果如下：(1) 率先使用自洽高斯近似（SCGA)）方法确定FeSe的阻挫磁相互作用[Y. Gu, J. Zhao* et al., Physical Review B 106, L060504 (2022)]；(2) 在FeSe1-xSx中发现中子自旋共振态，发现自旋激发和向列序以及超导电性的强耦合[D. Hu, J. Zhao* et al., Physical Review B 106, 214522 (2022)] ; (3) 率先确定重电子掺杂铁硒类超导体Li0.8Fe0.2ODFeSe超导共振模的各向同性自旋激发 [D. Hu, J. Zhao* et al., Journal of Physics: Condensed Matter 33, 45LT01 (2021)]； (4) 首次在重空穴掺杂的KFe2As2超导体中发现自旋共振态 [S. Shen, J. Zhao* et al., Physical Review Letters 124, 017001 (2020)]；（5）揭示铬基超导体母体的阻挫磁相互作用和淬灭自旋涨落[Y. Qin, J. Zhao* et al., Chinese Physics Letters 39, 127501 (2022)]。