铜氧超导材料电荷密度波和元激发的共振非弹性X射线散射研究

Resonant inelastic X-ray scattering study of charge density waves and elementary excitations in cuprate superconductors

铜氧超导材料问世以来,其高温超导的理论机制仍有待解决.近年来,铜氧超导领域的实验进展主要集中在利用新型表征手段探索微观机理,其中同步辐射的建设推进了先进谱学技术的发展.基于同步辐射的共振非弹性X射线散射技术,因具有体测量、能量动量分辨及直接探测不同元激发色散关系的能力,在铜氧超导材料研究中得到了广泛应用.无论是B ardeen-Cooper-Schrieffer理论框架下粘合库珀对的声子,还是强关联体系中Hubbard模型预测的磁涨落和竞争序,都可以用共振非弹性X射线散射实验测量,并研究它们之间的关联.本文介绍了利用共振非弹性X射线散射测量铜氧超导材料电荷密度波及相关低能激发,包括声子异常现象的研究进展,还介绍了磁激发和超导最高转变温度的关系,最后对未来的研究方向和面临的挑战进行展望.

In the 38 years since the discovery of cuprate superconductors,the theoretical mechanism of hightemperature superconductivity remains unresolved.Recent experimental progress has focused on exploring microscopic mechanisms by using novel characterization techniques.The development of synchrotron radiation has driven significant progress in spectroscopic methods.Resonant inelastic X-ray scattering(RIXS),based on synchrotron radiation,has been widely used to study cuprate superconductors due to its ability to perform bulk measurements,provide energy-momentum resolution,and directly probe various elemental excitations.The RIXS can measure phonons,which bind Cooper pairs in the BCS theory,and magnetic fluctuations and competing orders predicted by the Hubbard model in strongly correlated systems,allowing for the study of their interrelationships.This paper reviews the progress in using RIXS to measure charge density waves and related low-energy excitations,including phonon anomalies,in cuprate superconductors.It also examines the relationship between magnetic excitation and the highest superconducting transition temperature,and provides prospects for future research directions and challenges.