Electronic Phase Separation in Iron Selenide(Li,Fe)OHFeSe Superconductor System

作     者：Yiyuan Mao Jun Li Yulong Huan Jie Yuan Zi-an Li Ke Chai Mingwei Ma Shunli Ni Jinpeng Tian Shaobo Lin Huaxue Zhou Fang Zhoul, Jianqi Lil, Guangming Zhang Kui Jin Xiaoli Dong Zhongxian Zhao 毛义元;李军;黄裕龙;袁洁;李子安;柴可;马明伟;倪顺利;田金鹏;刘少博;周花雪;周放;李建奇;张广铭;金魁;董晓莉;赵忠贤

作者机构：Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 University of Chinese Academy of Sciences Beijing 100049 Key Laboratory for Vacuum Physics University of Chinese Academy of Sciences Beijing 100049 Research Institute of Superconductor Electronic Nanjing University Nanjing 210093 School of Physics Beijing Institute of Technology Beijing 100081 State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics Tsinghua University Beijing 100084 

出 版 物：《Chinese Physics Letters》 (中国物理快报（英文版）)

年 卷 期：2018年第35卷第5期

页      面：123-128页

核心收录：

学科分类：080801[工学-电机与电器] 0808[工学-电气工程] 08[工学] 0805[工学-材料科学与工程（可授工学、理学学位）] 080502[工学-材料学] 

基　　金：Supported by the National Key Research and Development Program of China under Grant Nos 2017YFA0303003,2016YFA0300300 and 2015CB921000 the National Natural Science Foundation of China under Grant Nos 11574370,11474338,11674374 and 61501220 the Strategic Priority Research Program and Key Research Program of Frontier Sciences of the Chinese Academy of Sciences under Grant Nos QYZDY-SSW-SLH001,QYZDY-SSW-SLH008 and XDB07020100 the Beijing Municipal Science and Technology Project under Grant No Z161100002116011 

主　　题：Li,Fe)OHFeSe Superconductor System Fe Electronic Phase Separation in Iron Selenide AFM 

摘      要：The phenomenon of phase separation into antiferromagnetic（AFM） and superconducting（SC） or normal-state regions has great implication for the origin of high-temperature（high-T_c） superconductivity. However, the occurrence of an intrinsic antiferromagnetism above the T_c of（Li,Fe）OHFe Se superconductor is questioned. Here we report a systematic study on a series of（Li,Fe）OHFe Se single crystal samples with T_c up to ～41 K. We observe an evident drop in the static magnetization at T_（afm） ～ 125 K, in some of the SC（T_c 38 K, cell parameter c■9.27 ？） and non-SC samples. We verify that this AFM signal is intrinsic to（Li,Fe）OHFe Se. Thus, our observations indicate mesoscopic-to-macroscopic coexistence of an AFM state with the normal（below T_（afm）） or SC（below T_c） state in（Li,Fe）OHFe Se. We explain such coexistence by electronic phase separation, similar to that in high-T_c cuprates and iron arsenides. However, such an AFM signal can be absent in some other samples of（Li,Fe）OHFe Se, particularly it is never observed in the SC samples of T_c 38 K, owing to a spatial scale of the phase separation too small for the macroscopic magnetic probe. For this case, we propose a microscopic electronic phase separation. The occurrence of two-dimensional AFM spin fluctuations below nearly the same temperature as T_（afm）, reported previously for a（Li,Fe）OHFe Se（T_c ～ 42 K） single crystal, suggests that the microscopic static phase separation reaches vanishing point in high T_c（Li,Fe）OHFe Se. A complete phase diagram is thus established. Our study provides key information of the underlying physics for high-T_c superconductivity.