Abstract
We investigate the electronic structure of BaMnBi2 and BaZnBi2 using angle-resolved photoemission spectroscopy and first-principles calculations. Although they share similar structural properties, we show that their electronic structure exhibit dramatic differences. A strong anisotropic Dirac dispersion is revealed in BaMnBi2 with a decreased asymmetry factor compared with other members of AMnBi2 (A = alkali earth or rare earth elements) family. In addition to the Dirac cones, multiple bands crossing the Fermi energy give rise to a complex Fermi surface topology for BaZnBi2. We further show that the strength of hybridization between Bi-p and Mn-d/Zn-s states is the main driver of the differences in electronic structure for these two related compounds.
Highlights
Dirac materials, characterized by the linear dispersion of their low-energy quasi-particle excitations, have received significant recent attention, given their potential to host various exotic phenomena such as high mobilities due to strongly suppressed backscattering, unconventional quantum Hall effects, and Klein tunneling[1,2]
Anisotropic Dirac materials are distinguished by their strong momentum-dependent Fermi velocities on the Dirac cone[4,5]
Investigating the role of the transition metal d-states on low energy Dirac dispersion is challenging due to the multi-valence nature of these ions; the change in the orbital occupancy may induce a variety of ordered states and accompanying atomic distortions
Summary
Ba on the A-site leads to anisotropic Dirac bands, with different asymmetry and anisotropy from (Ca,Sr). First-principles DFT calculations within the generalized gradient approximation (GGA) and including spin-orbit (SO) interactions, shown with black solid lines on Fig. 2a, predict dispersion consistent with the experimental data To analyze these anisotropic Dirac bands further, we examine the measured electronic band dispersion along four cuts from A to D (Fig. 2b). We have investigated the electronic structure of BaMnBi2 and BaZnBi2 using ARPES and first-principles calculations, focusing on the effect of substituting A-site cation with larger ionic radius and the role of the transition metal states on the band dispersion near EF. Compared with the isostructural compound SrMnBi2, substitution of the A-site cation with larger ionic radius results in a small decrease in the spin-orbit induced asymmetry and negligible change in the anisotropy of the Dirac cone, and maintains the same Fermi surface topology originating with the Bi-p states from the square net.
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