铁砷化物超导体的自旋激发谱  

Spin excitation spectra of iron pnictide superconductors

作　　者：李泽众 洪文山 谢涛 刘畅 罗会仟[1] LI Zezhong;HONG Wenshan;XIE Tao;LIU Chang;LUO Huiqian(Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China;University of Chinese Academy of Sciences,Beijing 100049,China;School of Physics,Sun Yat-Sen University,Guangzhou 510275,China)

机构地区：[1]中国科学院物理研究所,北京100190 [2]中国科学院大学,北京100049 [3]中山大学物理学院,广州510275

出　　处：《物理学报》2025年第1期63-77,共15页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2023YFA1406100,2018YFA0704200);中国科学院战略性先导科技专项(B类)(批准号:XDB25000000,XDB33000000,GJTD-2020-01)资助的课题.

摘　　要：铁基超导体的多结构体系和丰富的磁性物理为理解非常规超导微观机理提供了广阔的平台,其中自旋涨落被认为是超导配对的最可能媒介.本文以铁砷化物超导体为例,系统总结了铁基超导体自旋激发谱的非弹性中子散射研究结果,并探讨了相关的普适规律;重点介绍了铁砷化物超导体中低能自旋激发与超导电性的直接联系,即中子自旋共振模的行为,以及高能自旋激发谱的色散关系、强度分布、总体磁矩等特征,并充分比较了与铜氧化物高温超导体的异同.Spin fluctuations are often considered the most likely candidates for superconducting electron pairing media in unconventional superconductors.The iron-based superconductors provide a wide range of opportunities for studying the mechanism of unconventional superconductivity,as they have many systems with different structures and rich magnetisms.Taking the iron pnictide superconductors for example,this review summarizes the inelastic neutron scattering results of the spin excitation spectrum of iron-based superconductors,especially for their common features.Firstly,we introduce the direct connection between the low-energy spin excitations and superconductivity,which is so called the neutron spin resonance mode.This mode widely exists in the superconducting states of all iron-based superconductors,where the resonance energy ER is linearly proportional to the critical temperature Tc:ER=4.9kBTc,and it has a universal c-axis preferred characteristic.The in-plane dispersion of spin resonance mode is not limited by the superconducting energy gap,which is in contrast to the traditional spin exciton model.The out-of plane dispersion of spin resonance mode is determined by the Fe-As interplanar distance,indicating that the three-dimensional spin correlation effect cannot be ignored,which may be the key to clarifying the role of spin fluctuations in superconductivity.Secondly,we summarize the energy dispersion,intensity distribution,and total fluctuating moment for high energy spin excitations.Although the Heisenberg model can roughly describe the similar dispersions in different systems based on the anisotropic in-plane nearest neighbor effective exchange couplings and the similar second nearest neighbor effective exchange coupling,the correlated Hubbard model based on itinerant magnetism can more accurately describe the spin wave behavior after degeneracy,thus the spin excitations are more likely to be understood from the perspective of itinerant magnetism.The spin excitation intensity varies greatly with energy in differ

关 键 词：铁基超导体 高温超导 非弹性中子散射 自旋激发谱 自旋涨落 

分 类 号：O511.3[一般工业技术—材料科学与工程]