1Center for High Pressure Science & Technology Advanced Research, Beijing 100094, China 2Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 3School of Physics, University of Chinese Academy of Sciences, Beijing 100190, China 4Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (Ministry of Education), School of Physics, Beijing Institute of Technology, Beijing 100081, China 5Xi'an Modern Chemistry Research Institute, Xi'an 710065, China 6High Pressure Collaborative Access Team (HPCAT), Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA 7Songshan Lake Materials Laboratory, Dongguan 523808, China 8Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
Abstract：Recently, a series of novel compounds Ba$_{3}$MX$_{5}$ (M = Fe, Ti, V; X = Se, Te) with hexagonal crystal structures composed of quasi-1-dimensional (1D) magnetic chains has been synthesized by our research team using high-pressure and high-temperature methods. The initial hexagonal phases persist to the maximum achievable pressure, while spin configurations and magnetic interactions may change dramatically as a result of considerable reductions in interchain separations upon pressurization. These compounds therefore offer unique possibilities for studying the evolution of intrinsic electronic structures in quasi-1D magnetic systems. Here we present a systematic investigation of Ba$_{9}$Fe$_{3}$Te$_{15}$, in which the interchain separations between trimerized 1D chains ($\sim $10.2 Å) can be effectively modulated by external high pressure. The crystal structure especially along the 1D chains exhibits an abnormal expansion at $\sim $5 GPa, which accompanies trimerization entangled anomalous mixed-high-low spin transition. An insulator-metal transition has been observed under high pressure as a result of charge-transfer gap closing. Pressure-induced superconductivity emerges at 26 GPa, where the charge-transfer gap fully closes, 3D electronic configuration forms and local spin fully collapses.
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2020, Vol. 37 
