KUJI QMAT Seminar #48 で招待講演をしました。

＜ 開催日時 ＞
　　Date: Oct. 31 (Thu), 2024
　　Time: 8:00 (UK), 9:00 (Italy), 17:00 (Korea and Japan),
　　duration: one hour (30 min + Q&A 30 min)

＜ 開催場所 ＞
　　オンライン形式

＜詳細ホームページ＞
　　https://trikuc.jp/

＜ 発表内容 ＞

” High-Temperature Superconductivity under Extreme Pressure: Hydrogen Sulfide “

Abstract:
The cooperation between theoretical and experimental investigation broke the record for superconducting critical temperature,Tc,  in sulfur hydride under high pressure at the end of 2014[1, 2, 3].  
By compression of hydrogen sulfide, H₂S, at low temperature 200 K, a superconducting phase named low-Tc phase appears above 100 GPa, and Tc increases up to 150 K with increased pressure to 200 GPa. 
High-T_c phase showing Tc ~ 200 K is obtained after annealing of the low-Tc phase near room temperature. 
Several theoretical groups proposed that H₂S dissociates into H3S and elemental sulfur, and the H₃S which has cubic symmetric structure shows the high-T_c over 200 K[2,3].
However, the phase boundary and the crystal structures above 50 GPa were not determined experimentally yet. Here I introduce our results of synchrotron X-ray diffraction studies on the superconducting phases in sulfur hydride. 
Our results suggest that H₂S dissociates into cubic-H3S and elemental sulfur under high pressure through 
metastable phases, and the maximum-Tc of H3S is 200 K [4, 5].

1. A. P. Drozdov et al., Nature, 525, 73 (2015).
2. Y. Li et al., J. Chem. Phys., 140, 174712 (2014).
3. D. Duan et al., Sci. Rep., 4, 6968 (2014).
4. M. Einaga et al., Nature Phys. 12, 835 (2016).
5. H. Nakao et al., J. Phys. Soc. Jpn. 88, 123701 (2019).