1
|
Szewczyk KA, Domagalska IA, Durajski AP, Szczęśniak R. Nonadiabatic superconductivity in a Li-intercalated hexagonal boron nitride bilayer. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2020; 11:1178-1189. [PMID: 32821642 PMCID: PMC7418097 DOI: 10.3762/bjnano.11.102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 07/08/2020] [Indexed: 06/11/2023]
Abstract
When considering a Li-intercalated hexagonal boron nitride bilayer (Li-hBN), the vertex corrections of electron-phonon interaction cannot be omitted. This is evidenced by the very high value of the ratio λωD/εF ≈ 0.46, where λ is the electron-phonon coupling constant, ωD is the Debye frequency, and εF represents the Fermi energy. Due to nonadiabatic effects, the phonon-induced superconducting state in Li-hBN is characterized by much lower values of the critical temperature (T LOVC C ∈ {19.1, 15.5, 11.8} K, for μ* ∈ {0.1, 0.14, 0.2}, respectively) than would result from calculations not taking this effect into account (T ME C∈ {31.9, 26.9, 21} K). From the technological point of view, the low value of T C limits the possible applications of Li-hBN. The calculations were carried out under the classic Migdal-Eliashberg formalism (ME) and the Eliashberg theory with lowest-order vertex corrections (LOVC). We show that the vertex corrections of higher order (λ3) lower the value of T LOVC C by a few percent.
Collapse
Affiliation(s)
- Kamila A Szewczyk
- Division of Theoretical Physics, Jan Długosz University in Częstochowa, Ave. Armii Krajowej 13/15, 42-200 Częstochowa, Poland
| | - Izabela A Domagalska
- Quantum Optics and Engineering Division, Faculty of Physics and Astronomy, University of Zielona Góra, Prof. Z. Szafrana 4a, 65-516 Zielona Góra, Poland
| | - Artur P Durajski
- Division of Physics, Częstochowa University of Technology, Ave. Armii Krajowej 19, 42-200 Częstochowa, Poland
| | - Radosław Szczęśniak
- Division of Theoretical Physics, Jan Długosz University in Częstochowa, Ave. Armii Krajowej 13/15, 42-200 Częstochowa, Poland
- Division of Physics, Częstochowa University of Technology, Ave. Armii Krajowej 19, 42-200 Częstochowa, Poland
| |
Collapse
|
2
|
Arita R, Koretsune T, Sakai S, Akashi R, Nomura Y, Sano W. Nonempirical Calculation of Superconducting Transition Temperatures in Light-Element Superconductors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29. [PMID: 28060417 DOI: 10.1002/adma.201602421] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 08/05/2016] [Indexed: 02/05/2023]
Abstract
Recent progress in the fully nonempirical calculation of the superconducting transition temperature (Tc ) is reviewed. Especially, this study focuses on three representative light-element high-Tc superconductors, i.e., elemental Li, sulfur hydrides, and alkali-doped fullerides. Here, it is discussed how crucial it is to develop the beyond Migdal-Eliashberg (ME) methods. For Li, a scheme of superconducting density functional theory for the plasmon mechanism is formulated and it is found that Tc is dramatically enhanced by considering the frequency dependence of the screened Coulomb interaction. For sulfur hydrides, it is essential to go beyond not only the static approximation for the screened Coulomb interaction, but also the constant density-of-states approximation for electrons, the harmonic approximation for phonons, and the Migdal approximation for the electron-phonon vertex, all of which have been employed in the standard ME calculation. It is also shown that the feedback effect in the self-consistent calculation of the self-energy and the zero point motion considerably affect the calculation of Tc . For alkali-doped fullerides, the interplay between electron-phonon coupling and electron correlations becomes more nontrivial. It has been demonstrated that the combination of density functional theory and dynamical mean field theory with the ab initio downfolding scheme for electron-phonon coupled systems works successfully. This study not only reproduces the experimental phase diagram but also obtains a unified view of the high-Tc superconductivity and the Mott-Hubbard transition in the fullerides. The results for these high-Tc superconductors will provide a firm ground for future materials design of new superconductors.
Collapse
Affiliation(s)
- Ryotaro Arita
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan
- JST ERATO Isobe Degenerate π-Integration Project, Advanced Institute for Materials Research, Tohoku University, Katahira, Aoba-ku, Sendai, 980-8577, Japan
| | - Takashi Koretsune
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan
- JST-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
| | - Shiro Sakai
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan
| | - Ryosuke Akashi
- Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Yusuke Nomura
- Centre de Physique Théorique, École Polytechnique, CNRS, Université Paris-Saclay, F-91128, Palaiseau, France
| | - Wataru Sano
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan
- Department of Applied Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| |
Collapse
|
3
|
Takada Y. Role of the ward identity and relevance of the G0W0 approximation in normal and superconducting states. Mol Phys 2016. [DOI: 10.1080/00268976.2015.1131860] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Yasutami Takada
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Japan
| |
Collapse
|