Charge density wave induced nodal lines in LaTe$_3$

TL;DR

This paper demonstrates that LaTe$_3$ hosts a Kramers nodal line protected by symmetries, revealed through ARPES and DFT, with implications for understanding topological features in charge density wave materials.

Contribution

The study identifies and characterizes a Kramers nodal line in LaTe$_3$, combining experimental ARPES data with theoretical DFT calculations to reveal symmetry-protected topological features.

Findings

Presence of a Kramers nodal line connecting TR invariant momenta.

Gapless crossings between CDW-induced shadow bands and main bands.

Spinless nodal lines gapped out by spin-orbit coupling.

Abstract

LaTe$_3$ is a noncentrosymmetric (NC) material with time reversal (TR) symmetry in which the charge density wave (CDW) is hosted by the Te bilayers. Here, we show that LaTe$_3$ hosts a Kramers nodal line (KNL), a twofold degenerate nodal line that connects the TR invariant momenta in NC achiral systems, using angle resolved photoemission spectroscopy (ARPES), density functional theory (DFT), effective band structure (EBS) calculated by band unfolding, and symmetry arguments. DFT incorporating spin-orbit coupling (SOC) reveals that the KNL -- protected by the TR and lattice symmetries -- imposes gapless crossings between the bilayer-split CDW-induced shadow bands and the main bands. In excellent agreement with the EBS, ARPES data corroborate the presence of the KNL and show that the crossings traverse the Fermi level. Furthermore, spinless nodal lines - entirely gapped out by the SOC - are formed by the linear crossings of the shadow and main bands with a high Fermi velocity.