Superconductivity and topological properties in the kagome metals CsM3Te5 ( M =Ti, Zr, Hf): A first-principles investigation

Abstract

Inspired by the discovery and fascinating properties of kagome metals $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$ ($A$= K, Rb, Cs), we investigate the superconductivity and topological properties of the $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$-prototype kagome materials $\mathrm{Cs}{M}_{3}{\mathrm{Te}}_{5}$ ($M$=Ti, Zr, Hf) using first-principles calculations. The calculated results of formation energy and phonon dispersion indicate that this family of kagome materials are stable and may be synthesized in experiments. By analytically solving the Allen-Dynes-modified McMillan formula, the superconducting critical temperatures for ${\mathrm{CsTi}}_{3}{\mathrm{Te}}_{5}, {\mathrm{CsZr}}_{3}{\mathrm{Te}}_{5}$, and ${\mathrm{CsHf}}_{3}{\mathrm{Te}}_{5}$ are predicted as 8.02, 5.47, and 3.51 K, respectively. The electron-phonon couplings are dominated by the coupling between the in-plane atomic vibrational modes and the in-plane electronic orbitals. In addition, the ${\mathrm{CsZr}}_{3}{\mathrm{Te}}_{5}$ and ${\mathrm{CsHf}}_{3}{\mathrm{Te}}_{5}$ can be categorized as ${\mathbb{Z}}_{2}$ topological metals according to the calculations of topological invariant and surface states. Such coexistence of superconductivity and nontrivial topological properties in ${\mathrm{CsZr}}_{3}{\mathrm{Te}}_{5}$ and ${\mathrm{CsHf}}_{3}{\mathrm{Te}}_{5}$ are beneficial to study the interaction between superconductivity and nontrivial band character.