Electron-phonon superconductivity and charge density wave instability in the layered titanium-based pnictide BaTi$_2$Sb$_2$O

TL;DR

This study uses first principles calculations to explore electron-phonon interactions and lattice instabilities in BaTi$_2$Sb$_2$O, revealing mechanisms for its superconductivity and charge density wave phase.

Contribution

It provides detailed phonon dispersion and electron-phonon coupling analysis, highlighting the origin of superconductivity and charge density wave in BaTi$_2$Sb$_2$O.

Findings

Weak lattice instability near zone corners causes charge-density wave.

Strong electron-phonon coupling, especially to in-plane Ti modes.

Large total coupling explains superconductivity in the compound.

Abstract

I present the results of first principles calculations of the phonon dispersions and electron-phonon coupling for BaTi$_2$Sb$_2$O. The phonon dispersions show a weak lattice instability near the zone corners that leads to a charge-density wave phase. The calculations of the electron-phonon coupling reveal strong coupling, especially to the in-plane Ti modes. The total coupling is large enough to readily explain the superconductivity in this compound. As the Fermi surfaces are disconnected with different orbital character weights, this compound is likely to host a multiband superconductivity.