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.

Bulk electronic structure of Ni2MnGa studied by density functional theory and hard x-ray photoelectron spectroscopy

“…A phason excitation was observed in the martensite phase of Ni 2 MnGa from a neutron scattering experiment that was related to a CDW state [20]. Evidence of modulation in the martensite phase of Ni 2 MnGa was also observed in electron and x-ray diffraction studies from the appearance of the satellite spots [17,25,26], as is well-known for chalcogenide materials that exhibit CDW [36,37]. From an ultraviolet photoemission spectroscopy (UPS) study [13], the existence of CDW in the premartensite phase [38] was shown on the surface of Ni 2 MnGa(100) that continued to exist also in the martensite phase.…”

Non-coplanar helimagnetism in the layered van-der-Waals metal DyTe3

“…Tellurium 5 p electrons are localized in Te 2 square net bilayers ( a c plane), in which they form dispersive bands with elevated Fermi velocity 16 , 19 – 21 . This quasi two-dimensional electronic structure amplifies correlation phenomena, such as the formation of charge density wave (CDW) order 22 and superconductivity 23 , 24 , while also hosting protected band degeneracies 16 , 25 . In view of intense research efforts on R Te 3 , it is remarkable that their magnetism has never been discussed in detail; in particular, no full refinement of magnetic structures is available 26 – 31 .…”