Pressure-Induced Metallization Accompanied by Elongated S–S Dimer in Charge Transfer Insulator NiS_2 |
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引用本文: | 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.Pressure-Induced Metallization Accompanied by Elongated S–S Dimer in Charge Transfer Insulator NiS_2[J].中国物理快报,2019(10). |
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作者姓名: | 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 |
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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.
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