Molecular Hydride Superconductor BiH<sub>4</sub> with <i>T</i><sub>c</sub> up to 91 K at 170 GPa
Pengfei Shan, Liang Ma, Xin Yang, Mei Li, Ziyi Liu, Jun Hou, Sheng Jiang, Lili Zhang, Lifen Shi, Pengtao Yang, Chuanlong Lin, Bosen Wang, Jianping Sun, Haizhong Guo, Yang Ding, Huiyang Gou, Zhongxian Zhao, Jinguang Cheng
Abstract
In pursuit of high- T c hydride superconductors, the molecular hydrides have attracted less attention because the hydrogen quasimolecules are usually inactive for superconductivity. Here, we report on the successful synthesis of a novel bismuth hydride superconductor C 2/ c -BiH 4 at pressures around 170–180 GPa. Its structure comprises bismuth atoms and elongated hydrogen molecules with a H–H bond length of 0.81 Å at 170 GPa, characterizing it as a typical molecular hydride. Transport measurements revealed the occurrence of superconductivity with T c up to 91 K at 170 GPa, as evidenced by a sharp drop of resistivity to zero and a characteristic downward shift of T c under magnetic fields. Calculations by density functional theory elucidate that both midfrequency H-derived phonons and low-frequency vibrations from Bi atoms are important for the strong electron–phonon coupling in BiH 4, differentiating it from most high- T c superconducting hydrides. Our work not only places C 2/ c -BiH 4 among the molecular hydride superconductors with the highest T c but also offers new directions for designing and synthesizing more high- T c hydride superconductors.