Dirac nodal lines in the quasi-one-dimensional ternary telluride TaPtTe5

A Dirac nodal-line phase as a quantum state of topological materials, usually occur in three-dimensional or, at least, two-dimensional materials with sufficient symmetry operations that could protect the Dirac band crossings. Here, we report a combined theoretical and experimental study on the electronic structure of the quasi-one-dimensional ternary telluride ${\mathrm{TaPtTe}}₅$, which is corroborated as being in a robust nodal-line phase with fourfold degeneracy. Our angle-resolved photoemission spectroscopy measurements show that two pairs of linearly dispersive Dirac-like bands exist in a very large energy window, which extend from a binding energy of $\ensuremath{\sim}0.75$ eV to across the Fermi level. The crossing points are at the boundary of Brillouin zone and form Dirac-like nodal lines. Using first-principles calculations, we demonstrate the existing of nodal surfaces on the ${k}_y=\ifmmode\pm\else\textpm\fi{}\ensuremath{\pi}$ plane in the absence of spin-orbit coupling (SOC), which are protected by nonsymmorphic symmetry in ${\mathrm{TaPtTe}}₅$. When SOC is included, the nodal surfaces are broken into several nodal lines. By theoretical analysis, we conclude that the nodal lines along $Y\text{\ensuremath{-}}T$ and the ones connecting the $R$ points are nontrivial and protected by nonsymmorphic symmetry against SOC.