Disentangling the electron-lattice dichotomy of the excitonic insulating phase in TaNi(SeS)with sulfur substitution and potassium deposition

作     者：Tongrui Li Yang Liu Hongen Zhu Haiping Chen Zhanfeng Liu Zhengming Shang Yuliang Li Hui Tian Yunbo Wu Yuhao Hong Haihua Luo Yi Liu Guobin Zhang Lidong Zhang Yuqiao Guo Changzheng Wu Li Song Shengtao Cui Zhe Sun 

作者机构：National Synchrotron Radiation Laboratory University of Science and Technology of China School of Chemistry and Materials Science University of Science and Technology of China School of Mechanics and Optoelectronic Physics Anhui University of Science and Technology CAS Key Laboratory of Strongly-coupled Quantum Matter Physics University of Science and Technology of China Collaborative Innovation Center of Advanced Microstructures 

出 版 物：《Science China(Physics,Mechanics & Astronomy)》 (中国科学:物理学 力学 天文学(英文版))

年 卷 期：2024年

核心收录：

学科分类：07[理学] 070205[理学-凝聚态物理] 0702[理学-物理学] 

基　　金：supported by the National Natural Science Foundation of China (Grant No. U2032153) the National Key R&D Program of China(Grant No. 2017YFA0402901) the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB25000000) the Innovation Program for Quantum Science and Technology (Grant No.2021ZD0302802) the Users with Excellence Program of Hefei Science Center of the Chinese Academy of Sciences (Grant No. 2021HSC-UE004) the Fundamental Research Funds for the Central Universities (Grant No. WK2310000104) 

摘      要：Ta2NiSe5is a promising candidate for hosting an excitonic insulator （EI） phase,a novel electronic state driven by electron-hole Coulomb ***,the role of electron-lattice coupling in the formation of the EI phase remains ***,we use angle-resolved photoemission spectroscopy （ARPES） to study the band structure evolution of Ta2Ni(Se1-xSx)5with sulfur substitution and potassium deposition,which modulate the band gap and the carrier concentration,*** find that the Ta 5d states originating from the bottom of the conduction band persist at the top of the valence band in the low-temperature monoclinic phase,indicating the importance of exciton condensation in opening the gap in the semi-metallic band *** also observe that the characteristic overlap between the conduction and valence bands can be restored in the monoclinic lattice by mild carrier injection,suggesting that the lattice distortion in the monoclinic phase is not the main factor for producing the insulating gap,but rather the exciton condensation in the electronic system is the dominant driving *** results shed light on the electron-lattice decoupling and the origin of the EI phase in Ta2Ni(Se1-xSx)5.