Electron-phonon coupling and superconductivity in $\alpha$-MoB${}_2$ as a function of pressure

Abstract

We have studied the lattice dynamics, electron-phonon coupling, and superconducting properties of $\alpha$-MoB${}_2$, as a function of applied pressure, within the framework of density functional perturbation theory using a mixed-basis pseudopotential method. We found that phonon modes located along the A$-$H, H$-$L, and L$-$A high-symmetry paths exhibit large phonon linewidths and contribute significantly to the electron-phonon coupling constant. Although linewidths are particularly large for the highest-frequency optical phonon modes (dominated by B vibrations), their contribution to the electron-phonon coupling constant is marginal. The latter is largely controlled by the acoustic low-frequency modes of predominantly Mo character. It was observed that at a pressure of $90$~GPa, where $\alpha$-MoB${}_2$ forms, the phonon-mediated pairing falls into the strong-coupling regime, and the estimate for the superconducting critical temperature $T_c$ agrees well with experimental observations. When further increasing the applied pressure, a reduction of $T_c$ is predicted, which correlates with a hardening of the acoustic low-frequency phonon modes and a decrease of the electron-phonon coupling parameter.

arXiv commentUpdated and accepted for publication version

References in corpus (12)

• Phonons and related properties of extended systems from density-functional perturbation theory
• Superconductivity of metallic boron in MgB_2
• Phonon dispersion and electron-phonon coupling in MgB_2 and AlB_2
• Al substitution in MgB2 crystals: influence on superconducting and structural properties
• Pressure-induced Superconductivity at 32 K in MoB2
• Lattice dynamics and electron-phonon coupling in transition metal diborides
• Structure and Superconductivity in Zr-Stabilized, Nonstoichiometric Molybdenum Diboride
• MoB2 under Pressure: Superconducting Mo Enhanced by Boron
• Electron-phonon coupling and two-band superconductivity of Al- and C-doped MgB2
• Point-contact Andreev-reflection spectroscopy in segregation-free Mg_{1-x}Al_{x}B_2 single crystals up to x=0.32
• Single crystal growth and properties of MgB2 and Mg(B1-xCx)2
• Nb-substitution suppresses the superconducting critical temperature of pressurized MoB${}_2$