Diverse electronic topography in a distorted kagome metal LaTi3Bi4

TL;DR

This work addresses how the distorted kagome metal LaTi3Bi4 hosts rich electronic structure features, including Dirac-like states, multiple van Hove singularities (VHSs), and Ti 3d–derived flat bands. The authors combine high-resolution ARPES with density functional theory (DFT) calculations to map bulk and surface bands, revealing VHSs at $E_F$-proximity and two flat bands coming from Ti $3d$ orbitals. Polarization-dependent ARPES combined with DFT assigns orbital characters to the VHSs as $d_{xy}$, $d_{yz}$, and $d_{x^{2}-y^{2}}$, and attributes the flat bands to interlayer interference within the Ti kagome motif. A pronounced anisotropy arises from crystal distortion that breaks sixfold symmetry, highlighting LaTi3Bi4 as a versatile platform for studying the interplay between geometry, topology, and electron correlation in the LnM3X4 family.

Abstract

Recent reports on a family of kagome metals of the form LnTi3Bi4 (Ln = Lanthanide) has stoked interest due to the combination of highly anisotropic magnetism and a rich electronic structure. The electronic structure near the Fermi level is proposed to exhibit Dirac points and van Hove singularities. In this manuscript, we use angle resolved photoemission spectroscopy measurements in combination with density functional theory calculations to investigate the electronic structure of a newly discovered kagome metal LaTi3Bi4. Our results reveal multiple van Hove singularities (VHSs) with one VHS located in the vicinity of the Fermi level. We clearly observe two flat bands, which originate from the destructive interference of wave functions within the Ti kagome motif. These flat bands and VHSs originate from Ti d orbitals and are very responsive to the polarization of the incident beam. We notice a significant anisotropy in the electronic structure, resulting from the breaking of six fold rotational symmetry in this material. Our findings demonstrate this new family of Ti based kagome material as a promising platform to explore novel emerging phenomena in the wider LnTi3Bi4 (Ln= lanthanide) family of materials.

Figures (3)

• Figure 1: (a) Bulk three-dimensional Brillouin zone (BZ) along with its projection on the (001) surface. (b) Experimental Fermi surface (FS) measured along the (001) direction using a photon energy of 95 eV and LH polarization. (c) DFT calculated bulk FS. The dotted red hexagon is used to represent the BZ with high-symmetry points as indicated on top of the image. ARPES measured band dispersion using a photon energy of 110 eV along the $\overline{\Gamma}$--$\overline{\text{M}}$--$\overline{\text{K}}'$--$\overline{\Gamma}$ high-symmetry directions with (d) LH polarization and (e) LV polarization. (f) DFT projected bulk band structure along the $\overline{\Gamma}$--$\overline{\text{M}}$--$\overline{\text{K}}'$--$\overline{\Gamma}$ high-symmetry directions. Green arrows indicate VHSs and red arrows indicate the flat bands. ARPES measurements were performed at the ALS beamline 4.0.3 and the SSRL beamline 5-2.
• Figure 2: Observation of flat bands. (a) Experimental band dispersion measured along the $\overline{\text{K}}'$--$\overline{\text{M}}$--$\overline{\text{K}}'$ high-symmetry direction using LH polarization and (b) LV polarization. (c) Experimental band dispersion measured along the $\overline{\text{K}}$--$\overline{\Gamma}$--$\overline{\text{K}}$ high-symmetry direction using LH polarization and (d) LV polarization. ARPES measurements were performed at the ALS beamline 4.0.3 using a photon energy of 110 eV and at a temperature of 11 K.
• Figure 3: Anisotropic electronic structure of LaTi$_3$Bi$_4$. (a) Experimental band dispersion measured along the $\overline{\text{M}}$--$\overline{\Gamma}$--$\overline{\text{M}}$ high-symmetry direction using a photon energy of 95 eV. (b) same data as in (a), but measured along the $\overline{\text{M}}'$--$\overline{\Gamma}$--$\overline{\text{M}}'$ high-symmetry direction. (c) Experimental band dispersion measured along the $\overline{\text{K}}$--$\overline{\Gamma}$--$\overline{\text{K}}$ high-symmetry direction using a photon energy of 95 eV. (d) same data as in (c), but measured along the $\overline{\text{K}}'$--$\overline{\Gamma}$--$\overline{\text{K}}'$ high-symmetry direction. ARPES measurements were performed at the SSRL beamline 5-2 at a temperature of 8 K using LH polarization.