Charge density wave induced nodal lines in LaTe3

Abstract

LaTe₃ is a non-centrosymmetric material with time reversal symmetry, where the charge density wave is hosted by the Te bilayers. Here, we show that LaTe₃ hosts a Kramers nodal line—a twofold degenerate nodal line connecting time reversal-invariant momenta. We use angle-resolved photoemission spectroscopy, density functional theory with an experimentally reported modulated structure, effective band structures calculated by band unfolding, and symmetry arguments to reveal the Kramers nodal line. Furthermore, calculations confirm that the nodal line imposes gapless crossings between the bilayer-split charge density wave-induced shadow bands and the main bands. In excellent agreement with the calculations, spectroscopic data confirm the presence of the Kramers nodal line and show that the crossings traverse the Fermi level. Furthermore, spinless nodal lines—completely gapped out by spin-orbit coupling—are formed by the linear crossings of the shadow and main bands with a high Fermi velocity.

Kramers nodal lines are doubly degenerate nodal lines connecting time-reversal invariant momenta, which are predicted to exist in achiral, non-centrosymmetric crystals with spin-orbit interactions. Here, the authors use ARPES and DFT to demonstrate signatures of Kramers nodal lines in a non-centrosymmetric charge density wave-hosting crystal.