Pressure induced semiconductor-semimetal-superconductor transition of magnesium hexaborides

Li Duan; Jing Su; Ning Gong; Biao Wan; Peng Chen; Pengyuan Zhou; Zhibin Wang; Zhiping Li; Lailei Wu

doi:10.1039/c9dt02813g

Pressure induced semiconductor-semimetal-superconductor transition of magnesium hexaborides

Dalton Trans. 2019 Oct 14;48(38):14299-14305. doi: 10.1039/c9dt02813g. Epub 2019 Aug 27.

Authors

Li Duan¹, Jing Su¹, Ning Gong¹, Biao Wan¹, Peng Chen¹, Pengyuan Zhou¹, Zhibin Wang², Zhiping Li², Lailei Wu³

Affiliations

¹ State Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China. wll@ysu.edu.cn.
² Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China.
³ State Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China. wll@ysu.edu.cn and Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China.

PMID: 31453996
DOI: 10.1039/c9dt02813g

Abstract

A thorough structural exploration was performed for MgB₆ combining the global structure searching method with first-principles calculations. Besides the known Cmcm phase, new phases, i.e. I4/mmm, C2/m-I, C2/m-II and P2₁/m, were predicted to be stable in the pressure range of 18-100 GPa. Unexpectedly, Cmcm-MgB₆ was found to be a semiconductor with an indirect band gap of 0.38 eV with the HSE06 functional, in good agreement with the experimental finding. I4/mmm-MgB₆ stabilized above 18 GPa exhibits semimetallic behaviour with a topological node-line near the Fermi level. Consequently, C2/m-I MgB₆ with a sandwich structure similar to MgB₂ is predicted to be a superconductor with a critical temperature (T_c) of 9.5 K. By analysing the electronic structure, the intriguing semiconductor-semimetal-superconductor transition may be ascribed to the delocalization of more B-p electrons in the boron sublattice. The novel functions uncovered for MgB₆ may inspire more efforts to discover materials with intriguing properties.