Volume 122, Number 4, May 2018
|Number of page(s)||7|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||27 June 2018|
Electron-phonon coupling and superconductivity in LiB1+xC1−x
1 Department of Microelectronics Science and Engineering, Faculty of Science, Ningbo University, Zhejiang 315211, China
2 College of Physics and Engineering, Qufu Normal University - Shandong 273165, China
Received: 8 February 2018
Accepted: 6 June 2018
By means of the first-principles density-functional theory calculation and Wannier interpolation, electron-phonon coupling and superconductivity are systematically explored for boron-doped LiBC (i.e., ), with x between 0.1 and 0.9. Hole doping introduced by boron atoms is treated through virtual-crystal approximation. For the investigated doping concentrations, our calculations show that the optimal doping concentration corresponds to 0.8. By solving the anisotropic Eliashberg equations, we find that LiB1.8C0.2 is a two-gap superconductor, whose superconducting transition temperature, Tc, may exceed the experimentally observed value of MgB2. Similar to MgB2, the two-dimensional bond-stretching E2g phonon modes along the line have the largest contribution to electron-phonon coupling. More importantly, we find that the first two acoustic phonon modes B1 and A1 around the midpoint of the line play a vital role for the rise of Tc in LiB1.8C0.2. The origin of strong couplings in B1 and A1 modes can be attributed to enhanced electron-phonon coupling matrix elements and softened phonons. It is revealed that all these phonon modes couple strongly with σ-bonding electronic states.
PACS: 74.70.Dd – Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.) / 74.20.Pq – Electronic structure calculations / 63.20.kd – Phonon-electron interactions
© EPLA, 2018
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