Probing the Electronic Band Gap of Solid Hydrogen by Inelastic X-Ray Scattering up to 90 GPa

• Published in: Physical review letters 2021-01, Vol.126 (3), p.036402-036402, Article 036402
• Main Authors: Li, Bing, Ding, Yang, Kim, Duck Young, Wang, Lin, Weng, Tsu-Chien, Yang, Wenge, Yu, Zhenhai, Ji, Cheng, Wang, Junyue, Shu, Jinfu, Chen, Jiuhua, Yang, Ke, Xiao, Yuming, Chow, Paul, Shen, Guoyin, Mao, Wendy L, Mao, Ho-Kwang
• Format: Article
• Language: English
• Subjects: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Densification; Diamonds; Electrical properties; Energy gap; Hydrogen; Inelastic scattering; Metallizing; pressure effects; Structure factor; Synchrotron radiation; Synchrotrons; X-ray scattering
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/physrevlett.126.036402

Metallization of hydrogen as a key problem in modern physics is the pressure-induced evolution of the hydrogen electronic band from a wide-gap insulator to a closed gap metal. However, due to its remarkably high energy, the electronic band gap of insulating hydrogen has never before been directly observed under pressure. Using high-brilliance, high-energy synchrotron radiation, we developed an inelastic x-ray probe to yield the hydrogen electronic band information in situ under high pressures in a diamond-anvil cell. The dynamic structure factor of hydrogen was measured over a large energy range of 45 eV. The electronic band gap was found to decrease linearly from 10.9 to 6.57 eV, with an 8.6 times densification (ρ/ρ_{0}∼8.6) from zero pressure up to 90 GPa.