激子绝缘体杂质态的研究
Exploring impurity state in excitonic insulators
蒋欢欢 1王锐1
作者信息
摘要
激子绝缘体作为电子-空穴束缚对——激子凝聚形成的宏观相干态,自开展其理论研究以来,一直未能在实际材料中找到明确证据证明激子绝缘体在实验中的实现.理论探究更多新奇体系、寻找更多可实现激子绝缘体的候选材料,仍是当前热门的研究课题.以杂质为探针,利用平均场理论以及T矩阵近似的方法,系统地探究了以半导体、普通半金属和狄拉克半金属为母体材料形成的激子绝缘体体系,发现非磁性杂质在激子绝缘体中具有拆对效应,诱导产生束缚态.对于以普通半金属和半导体为母体材料的激子绝缘体,带内及带间杂质散射对束缚态能级位置及数目具有显著调制效应.相较之下,以狄拉克半金属为母体材料的激子绝缘体中的束缚态能级几乎不受杂质散射的影响.此外,杂质束缚态在三种不同母体激子绝缘体中表现出截然不同的能量特征,在普通半金属和半导体的激子绝缘体中可以产生能量较低的能隙间束缚态,且前者能量更低,而以狄拉克半金属为母态的激子绝缘体中的束缚态能级紧靠能隙边缘.
Abstract
As a macroscopic coherent state formed by the condensation of electron-hole bound pairs-excitons,excitonic insulators still lack clear experimental evidence for their realization in actual materials since the commencement of theoretical research on them.Therefore,the theoretical exploration of more novel systems and the search for more candidate materials that can realize excitonic insulators are still hot topics in current research.In this paper,we systematically investigated the excitonic insulators generated from parent materials such as semiconductors,normal semimetals,and Dirac semimetals.Using impurities as probes,utilizing mean-field theory as well as the T-matrix approximation,we found that nonmagnetic impurities have pair-breaking effect in excitonic insulators,inducing the generation of bound states.For excitonic insulators based on parent materials of normal semimetals and semiconductors,the intra-band and inter-band impurity scattering strength has a significant modulation effect on the numerical value and number of bound state energy levels.In contrast,the bound state energy levels in excitonic insulations with Dirac semimetals as the parent materials are hardly affected by impurity scattering.In addition,the impurity induced bound states show very different energy characteristics in the three different excitonic insulators.Lower energy inter-gap bound states can be produced in the excitonic insulators generated from normal semimetals than semiconductors,while the excitonic insulators generated from the Dirac semimetals have bound states tightly situated near the band-gap edge.
关键词
激子绝缘体/杂质散射效应/平均场理论/T矩阵近似Key words
excitonic insulator/impurity scattering effect/mean-field theory/T-matrix approximation引用本文复制引用
出版年
2024
国家科技期刊平台
NSTL
万方数据