Electron–phonon interaction and superconductivity in the

Abstract

Based on first-principles pseudopotential plane-wave method within the generalised gradient approximation, we have studied the structural, electronic, vibrational and BCS superconducting properties of . The calculated electronic properties for depict three-dimensional rather than two-dimensional characteristics in spite of the apparent two-dimensionality in its atomic structure. At the zone centre only three (La–La optical) and the single (Ni–Ni optical) phonon modes couple strongly with electrons. However, a critical assessment of the Eliashberg spectral function throughout the Brillouin zone reveals that all phonon modes except the two highest frequency phonon modes couple considerably with the electrons at the Fermi energy. By integrating the Eliashberg spectral function, the values of the average electron–phonon coupling constant and the logarithmic average frequency are found to be 0.73 and 301.23 K, respectively. Inserting these values into the Allen–Dynes formula with using a reasonable value of = 0.10 for the effective Coulomb repulsion parameter, the value of superconducting transition temperature is found to be 11.61 K which compares well with its experimental values of 12–13 K and 11.7 K.

Keywords:

• Density functional theory
• electronic structure
• phonons
• superconductivity
• ab initio
• boronitride

Acknowledgements

Some of the calculations for this project were carried out using the computing facilities on the Intel Nehalem (i7) cluster (ceres) in the School of Physics, University of Exeter, United Kingdom.

Notes

No potential conflict of interest was reported by the authors.