铁基超导体BaFe2-xNixAs2中磁性相互作用的中子散射  

Neutron scattering studies on the magnetic interaction in iron-based superconductor BaFe_(2-x)Ni_xAs_2

作　　者：罗会仟[1] 

机构地区：[1]中国科学院物理研究所,北京凝聚态物理国家实验室,北京100190

出　　处：《科学通报》2017年第34期3955-3966,共12页Chinese Science Bulletin

基　　金：国家重点基础研究发展计划(2011CBA00110,2012CB821400,2015CB921302);国家自然科学基金(11004233,11374011,91221303,11611130165);中国科学院战略性先导科技专项(B类)(XDB07020300);中国科学院青年创新促进会(2016004)资助

摘　　要：铁基超导电性起源于对母体中长程反铁磁序的压制,理解其超导微观机理的关键在于清楚认识磁性相互作用的演化规律,及其与超导电性的具体关系.本文以典型的电子型掺杂铁基超导体系BaFe_(2-x)Ni_xAs_2为对象,介绍了中子散射实验针对其电子态相图、磁有序态、低能磁激发和高能自旋涨落谱等磁性物理的相关研究,着重总结它们随掺杂的系统而演变的规律,同时介绍了在自旋向列相中的最新研究进展.最后,基于这些结果,提出了磁性相互作用驱动的非常规铁基超导电性的可能物理图像.Iron-based superconductivity emerges from the suppression of the long-ranged antiferromagnetic order in the parent compounds. To solve the microscopic mechanism of the superconductivity, the key issue is fully understanding about the evolution of magnetic interaction and its relationship between superconductivity. Here, we take the electron-doped iron-based superconductor BaFe（2-x）NixAs2 as atypical example, and summarize the neutron scattering results on the electronic phase diagram, magnetic ordered state, low-energy spin excitations and high-energy spin fluctuations, particularly for their systematic evolution versus electron dopings and the recent progress on the spin nematicity. Firstly, we will introduce about the crystal structure and magnetic structure, detailed procedure of the single crystal growth is also presented. By focusing on the structural transition temperature（Ts） and magnetic transition temperature（TN） near the optimal doping level, we have found both Ts and TN vanish above the superconducting transition temperature（Tc） as a first order manner, due to the lattice distortion and magnetically ordered moment decrease beyond the lower limit of the instrument resolution, giving an avoid quantum critical point at the optimal doping. In addition, the magnetic order becomes incommensurate and short-ranged magnetic cluster and competes with superconducting order, suggesting strong interplay between magnetism and superconductivity. Secondly, we will discuss about the itinerant magnetism and spin resonance mode at low energy for spin dynamics. The spin resonance mode in iron pnictides is explained as the collective quasiparticle excitations from the Fermi surface nesting between the hole pocket at the Γ point and electron pocket at the M point. This requires itinerant magnetism from the electrons near Fermi surfaces, which is further confirmed by neutron scattering by discovering the longitudinal mode and line shape change of low-energy spin excitations upon doping. Thirdly, we will pres

关 键 词：铁基超导 中子散射 磁有序 磁激发 自旋涨落 

分 类 号：O511.3[一般工业技术—材料科学与工程]