摘要
The insulator-metal transition triggered by pressure in charge transfer insulator NiS2 is investigated by combining high-pressure electrical transport,synchrotron x-ray diffraction and Raman spectroscopy measurements up to40-50 GPa.Upon compression,we show that the metallization firstly appears in the low temperature region at^3.2 GPa and then extends to room temperature at^8.0 GPa.During the insulator-metal transition,the bond length of S-S dimer extracted from the synchrotron x-ray diffraction increases with pressure,which is supported by the observation of abnormal red-shift of the Raman modes between 3.2 and 7.1 GPa.Considering the decreasing bonding-antibonding splitting due to the expansion of S-S dimer,the charge gap between the S-ppπ* band and the upper Hubbard band of Ni-3 d eg state is remarkabl.y decreased.These results consistently indicate that the elongated S-S dimer plays a predominant role in the insulator-metal transition under high pressure,even though the p-d hybridization is enhanced simultaneously,in accordance with a scenario of charge-gap-controlled type.
The insulator-metal transition triggered by pressure in charge transfer insulator NiS2 is investigated by combining high-pressure electrical transport,synchrotron x-ray diffraction and Raman spectroscopy measurements up to40-50 GPa.Upon compression,we show that the metallization firstly appears in the low temperature region at～3.2 GPa and then extends to room temperature at～8.0 GPa.During the insulator-metal transition,the bond length of S-S dimer extracted from the synchrotron x-ray diffraction increases with pressure,which is supported by the observation of abnormal red-shift of the Raman modes between 3.2 and 7.1 GPa.Considering the decreasing bonding-antibonding splitting due to the expansion of S-S dimer,the charge gap between the S-ppπ* band and the upper Hubbard band of Ni-3 d eg state is remarkabl.y decreased.These results consistently indicate that the elongated S-S dimer plays a predominant role in the insulator-metal transition under high pressure,even though the p-d hybridization is enhanced simultaneously,in accordance with a scenario of charge-gap-controlled type.
作者
吴昊
周永惠
袁亦方
陈春华
周颖
张博文
陈绪亮
顾川川
安超
王舒阳
戚梦瑶
张冉冉
张丽丽
李新建
杨昭荣
Hao Wu;Yong-Hui Zhou;Yi-Fang Yuan;Chun-Hua Chen;Ying Zhou;Bo-Wen Zhang;Xu-Liang Chen;Chuan-Chuan Gu;Chao An;Shu-Yang Wang;Meng-Yao Qi;Ran-Ran Zhang;Li-Li Zhang;Xin-Jian Li;Zhao-Rong Yang(Department of Physics and Laboratory of Material Physics,Zhengzhou University,Zhengzhou 450052;Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions,High Magnetic Field Laboratory,Chinese Academy of Sciences,Hefei 230031;University of Science and Technology of China,Hefei 230026;Institutes of Physical Science and Information Technology,Anhui University,Hefei 230601;Shanghai Synchrotron Radiation Facility,Shanghai Advanced Research Institute,Chinese Academy of Sciences,Shanghai 201204)
基金
Supported by the National Key Research and Development Program of China under Grant Nos 2018YFA0305700 and2016YFA0401804
the National Natural Science Foundation of China under Grant Nos 11574323,11704387,11874362,11804344,11804341,61774136,11605276 and U1632275
the Major Program of Development Foundation of Hefei Center for Physical Science and Technology under Grant No 2018ZYFX002
the Users with Excellence Project of Hefei Science Center of Chinese Academy of Sciences under Grant No 2018HSC-UE012
the Natural Science Foundation of Anhui Province under Grant Nos 1808085MA06,1908085QA18 and 1708085QA19
the Director’s Fund of Hefei Institutes of Physical Science of Chinese Academy of Sciences under Grant No YZJJ201621
