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 TaPtTe5, 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 similar to 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) = +/-pi plane in the absence of spin-orbit coupling (SOC), which are protected by nonsymmorphic symmetry in TaPtTe5. When SOC is included, the nodal surfaces are broken into several nodal lines. By theoretical analysis, we conclude that the nodal lines along Y-T and the ones connecting the R points are nontrivial and protected by nonsymmorphic symmetry against SOC.

Automated summary

This study investigates the electronic structure of ternary telluride TaPtTe5 and identifies a robust nodal-line phase with fourfold degeneracy. Experimental measurements reveal the existence of linearly dispersive Dirac-like bands in a large energy window, forming nodal lines crossing the Fermi level. Theoretical calculations demonstrate the protection of nodal surfaces in the absence of spin-orbit coupling and the breakdown of these surfaces into nodal lines when spin-orbit coupling is included.