Electron-Phonon Interaction in NbB_2 : A Comparison with MgB_2

TL;DR

This study compares the electron-phonon interactions in NbB_2 and MgB_2 using density-functional methods, revealing differences in their electronic and phononic properties that influence their superconducting transition temperatures.

Contribution

It provides a detailed computational comparison of electron-phonon interactions in NbB_2 and MgB_2, highlighting the factors affecting their superconductivity.

Findings

MgB_2 has a higher electron-phonon coupling constant than NbB_2.

MgB_2 exhibits a higher superconducting transition temperature (~22 K) compared to NbB_2 (~3 K).

Significant differences in electronic structure and phonon density of states between the two compounds.

Abstract

We present a comparison of electron-phonon interaction in NbB_2 and MgB_2, calculated using full-potential, density-functional-based methods in P6/mmm crystal structure. Our results, described in terms of (i) electronic structure, (ii) phonon density of states F(\omega), (iii) Eliashberg function \alpha ^2F(\omega), and (iv) the solutions of the isotropic Eliashberg gap equation, clearly show significant differences in the electron-phonon interaction in NbB_2 and MgB_2. We find that the average electron-phonon coupling constant \lambda is equal to 0.59 for MgB_2 and 0.43 for NbB_2, leading to superconducting transition temperature T_c of around 22 K for MgB_2 and 3 K for NbB_2.