Topological and superconducting properties in YD3 ( D=In , Sn, Tl, Pb)

Abstract

Using first-principles calculations, we explore the electron properties of ${\text{Y}D}_{3}$ ($D=\text{In}$, Sn, Tl, Pb) and predict that ${\mathrm{YIn}}_{3}$, ${\mathrm{YTl}}_{3}$, and ${\mathrm{YPb}}_{3}$ are topological superconductor candidates. In the presence of spin-orbit coupling effect, continuous band gaps for ${\mathrm{YIn}}_{3}$, ${\mathrm{YSn}}_{3}$, and ${\mathrm{YPb}}_{3}$ are opened between their highest occupied bands ($N$) and the lowest unoccupied bands ($N+1$), where the different ${Z}_{2}$ invariants are obtained. Differently and specially, there are type-II Dirac points (DPs) at the high-symmetry lines in ${\mathrm{YTl}}_{3}$, indicating one possibility of topological Dirac semimetal. Furthermore, the nontrivial Rashba-like topological surface states are achieved at the $\overline{\mathrm{X}}$ point on the (001) surface for ${\mathrm{YIn}}_{3}$, ${\mathrm{YTl}}_{3}$, and ${\mathrm{YPb}}_{3}$, as well as the Fermi arcs in ${\mathrm{YTl}}_{3}$ connecting the DPs. In addition to the topological properties, our electron-phonon coupling calculations indicate clearly that these four intermetallics are all phonon-mediated superconductors. The calculated superconducting transition temperatures of ${T}_{c}=0.96$, 6.34, 2.17, and 4.37 K respectively for ${\mathrm{YIn}}_{3}$, ${\mathrm{YSn}}_{3}$, ${\mathrm{YPb}}_{3}$, and ${\mathrm{YTl}}_{3}$ agree well with experiments.