Significant Progress Has Been Made in the Field of Superconducting Physics

Date:15-03-2021   |   【Print】 【close

In 2015, Nature published an article reporting that a superconducting critical temperature of more than 200K was found in the sulfur hydride. In 2018, LaH10 created a superconducting critical temperature record of 260K. Subsequently, theoretical research predicted that differing from the sulfur hydride containing S-H polar covalent bonds, metal hydrides containing hydrogen clusters can also achieve superconducting transitions of more than 200K, and even room temperature superconductivity. Although hydrides have become one of the most promising materials for realizing room temperature superconductivity, in rare earth metal hydrides that actually contain 4f or 5f electrons, superconductivity near room temperature has not been observed. In particular, there are few studies on its complex electronic structure and strong correlation effects. 

Focusing on the issues above, the research team of Prof. ZHONG Guohua from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences, in collaboration with Harbin Institute of Technology (Shenzhen) and Yantai University, focus on the rare earth metal terbium (Tb) containing 4f electrons, and explore the possibility of terbium hydride with different chemical ratios becoming room temperature superconductors. Research results were also published in Journal of Physical Chemistry C titled Cage Structure and Near Room-Temperature Superconductivity in TbHn(n = 1-12). 

Based on high-throughput calculations and first-principles material design, the research team found that the TbHn (n=1~12) system can achieve superconducting transformation in the pressure range of 0~350GPa. The results show that in the binary rare earth hydride formed by Tb and H, in a system with a series of chemical ratios such as TbH4, TbH5, TbH6, TbH9, TbH10, TbH12, the hydrogen atoms are combined into a cage structure and exhibit high-temperature superconductivity,indicating that the cage structure is of great significance for increasing the superconducting transition temperature. In particular, the TbH10 structure phase achieves a superconducting transition of about 280K under a pressure of 250 GPa, and becomes a near-room temperature superconductor that truly contains 4f electrons in rare earth metal hydrides. The study also discussed in-depth the strong correlation effect of 4f electrons under pressure and the contribution of 4f electrons to electron-phonon interactions. It pointed out that the superconducting mechanism of the high-temperature superconductor comes from the local-to- itinerant transition of the 4f electronic states under high pressure, and the resonance coupling caused by its movement in the sub-lattice of hydrogen atoms. 

The first author on the paper was a master student HAI Yulong, the co-corresponding author was professor ZHONG Guohua.  

Funding: National Natural Science Foundation of China and Shenzhen Basic Research Program. 

 

Figure. Left: crystal structure of TbH10-Fm3m and superconducting transition temperatures of Tb-H compounds. Right: phonon spectrum, phonon density of states, Eliashberg spectral function α2F (ω) and electron-phononcoupling  integral of TbH10-Fm3m at 250 GPa. (Image by SIAT) 

 

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SUN Lujia 

Email: lj.sun@siat.ac.cn 

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Cage Structure and Near Room-Temperature Superconductivity in TbHn (n = 1–12)