Dirac nodal lines in the quasi-one-dimensional ternary telluride TaPtTe$_5$

TL;DR

This study combines theoretical calculations and experimental measurements to reveal that the quasi-one-dimensional telluride TaPtTe$_5$ hosts a robust topological nodal-line phase with protected Dirac-like crossings, expanding understanding of topological states in low-dimensional materials.

Contribution

It provides the first detailed investigation of the topological nodal-line phase in TaPtTe$_5$, demonstrating the existence of protected nodal lines and surfaces influenced by nonsymmorphic symmetry and spin-orbit coupling.

Findings

TaPtTe$_5$ exhibits Dirac-like nodal lines extending across a large energy window.

Nodal surfaces on the $k_y = ext{±}\pi$ plane are protected by nonsymmorphic symmetry without SOC.

SOC breaks nodal surfaces into nodal lines, some of which are topologically protected.

Abstract

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 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 $\sim$ 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 $k_y = \pm \pi$ plane in the absence of spin-orbit coupling (SOC), which are protected by nonsymmorphic symmetry in 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 $Y$-$T$ and the ones connecting the $R$ points are non-trivial and protected by nonsymmorphic symmetry against SOC.