Electron-phonon coupling and superconductivity in an alkaline earth hydride CaH6 at high pressuresopen access
- Authors
- Jeon, Hyunsoo; Wang, Chongze; Liu, Shuyuan; Bok, Jin Mo; Bang, Yunkyu; Cho, Jun-Hyung
- Issue Date
- Aug-2022
- Publisher
- IOP Publishing Ltd
- Keywords
- superconductivity; alkaline earth; superhydride
- Citation
- NEW JOURNAL OF PHYSICS, v.24, no.8, pp.1 - 10
- Indexed
- SCIE
SCOPUS
- Journal Title
- NEW JOURNAL OF PHYSICS
- Volume
- 24
- Number
- 8
- Start Page
- 1
- End Page
- 10
- URI
- https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/172594
- DOI
- 10.1088/1367-2630/ac8a0c
- ISSN
- 1367-2630
- Abstract
- Recently, an alkaline earth hydride CaH6 having a sodalitelike clathrate structure has been experimentally synthesized at megabar pressures with a maximum T (c) of 215 K, comparable to that of a rare earth hydride LaH10. Here, based on first-principles calculations, we find that CaH6 exhibits a huge peak in the Eliashberg spectral function alpha (2) F around the low-frequency region of H-derived phonon modes, in contrast to LaH10 having a widely spreading spectrum of alpha (2) F over the whole frequencies of H-derived phonon modes. It is revealed that the huge peak of alpha (2) F in CaH6 is associated with an effective electron-phonon coupling (EPC) between low-frequency optical phonons and hybridized H 1s and Ca 3d states near the Fermi energy. As pressure increases, the strengthened H-H covalent bonding not only induces a hardening of optical phonon modes but also reduces the electron-phonon matrix elements related to the low-frequency optical modes, thereby leading to a lowering of the EPC constant. It is thus demonstrated that H-derived low-frequency phonon modes play an important role in the pressure-induced variation of T (c) in CaH6. Furthermore, unlike the presence of two distinct superconducting gaps in LaH10, CaH6 is found to exhibit a single isotropic superconducting gap.
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