Electron-phonon coupling and superconductivity in LiB1+xC1-x
Abstract
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., \text{LiB}1+x\text{C}1-x ), 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, T c , may exceed the experimentally observed value of MgB2. Similar to MgB2, the two-dimensional bond-stretching E 2g phonon modes along the Γ\text-A line have the largest contribution to electron-phonon coupling. More importantly, we find that the first two acoustic phonon modes B 1 and A 1 around the midpoint of the K\text-Γ line play a vital role for the rise of T c in LiB1.8C0.2. The origin of strong couplings in B 1 and A 1 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.
- Publication:
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EPL (Europhysics Letters)
- Pub Date:
- May 2018
- DOI:
- 10.1209/0295-5075/122/47001
- arXiv:
- arXiv:1801.07119
- Bibcode:
- 2018EL....12247001L
- Keywords:
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- Condensed Matter - Superconductivity;
- Condensed Matter - Materials Science
- E-Print:
- 7 pages, 10 figures, accepted for publication in EPL