Type-I antiferromagnetic Weyl semimetal ${\mathrm{InMnTi}}_{2}$

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Type-I antiferromagnetic Weyl semimetal ${InMnTi}_{2}$

Davide Grassano, Luca Binci, and Nicola Marzari

Phys. Rev. Research 6, 013140 – Published 2 February 2024

Abstract

Topological materials have been a main focus of studies in the past decade due to their protected properties that can be exploited for the fabrication of new devices. Among them, Weyl semimetals are a class of topological semimetals with nontrivial linear band crossings close to the Fermi level. The existence of such crossings requires the breaking of either time-reversal $(T)$ or inversion $(I)$ symmetry and is responsible for the exotic physical properties. In this work we identify the full-Heusler compound ${InMnTi}_{2}$ , as a promising, easy to synthesize, $T$ - and $I$ -breaking Weyl semimetal. To correctly capture the nature of the magnetic state, we employed a novel $DFT + U$ computational setup where all the Hubbard parameters are evaluated from first principles; thus preserving a genuinely predictive ab initio character of the theory. We demonstrate that this material exhibits several features that are comparatively more intriguing with respect to other known Weyl semimetals: the distance between two neighboring nodes is large enough to observe a wide range of linear dispersions in the bands, and only one kind of such node's pairs is present in the Brillouin zone. We also show the presence of Fermi arcs stable across a wide range of chemical potentials. Finally, the lack of contributions from trivial points to the low-energy properties makes the materials a promising candidate for practical devices.

Received 27 October 2023
Accepted 22 December 2023

DOI:https://doi.org/10.1103/PhysRevResearch.6.013140

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Density of states Edge states Electronic structure Electronic structure of atoms & molecules Fermi surface First-principles calculations Surface states Topological materials

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Davide Grassano ^* and Luca Binci

Theory and Simulations of Materials (THEOS), and National Center for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland

Nicola Marzari

Theory and Simulations of Materials (THEOS), and National Center for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland and Laboratory for Materials Simulations (LMS), Paul Scherrer Institut (PSI), CH-5232, Villigen PSI, Switzerland

^*davide.grassano@epfl.ch

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Vol. 6, Iss. 1 — February - April 2024

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Figure 1
(a) Band structure along the high-symmetry path. (b) Plot of the Fermi surface obtained from a Wannier interpolation on a $151 \times 151 \times 151 k$ -point grid. The Fermi surface shows pockets surrounding the 12 pairs of WNs. Only one other pocket of trivial points is present around $Γ$ . (c) Plot of the BZ including the position of the WNs in the antiferromagnetic ground state. The nodes with chirality $+ 1$ are shown in red, while the one with chirality $- 1$ are shown in blue. The green lines show the high-symmetry path on which the bands have been calculated.
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Figure 2
Plot of the DFT (dashed blue) and Wannier (red) band dispersion in proximity of a Weyl node. The $W \to W x$ direction is set to line that joins a pair of adjacent Weyl nodes. The $y$ and $z$ directions are chosen to be perpendicular to $x$ and each other with $y$ lying in the $x y$ plane.
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Figure 3
Plot of the DOS near the Fermi level computed from a Wannier interpolation on a $151 \times 151 \times 151 k$ -point grid with a gaussian smearing of 1 meV. The inset shows a zoom in an energy range closer to the Fermi level; in green is the fit of the DOS near the WN using a quadratic polynomial for the expected 60 meV range. The DOS has a minimum at $- 0.096$ meV, which is the expected position of the WNs with respect to the Fermi level. The fact that the DOS does not go to zero is the consequence of the presence of the pocket at $Γ$ , but the expected quadratic behavior is still clearly present.
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Figure 4
(a) Plot of the computed imaginary part of the dielectric function. (b) Plot of the real part of the optical conductivity. In green, the results of the linear fit starting from the onset energy given by $2 E_{w}$ . The plots show that the low-energy excitation properties fully agree with the model for a type-I WS. Indeed, we observe that real part of the optical conductivity can be fitted with a linear dispersion starting from an onset of 150 meV in a range wider than the expected 60 meV.
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Figure 5
Surface states computed with the iterative Green's function method on top of the Wannierization for both the titanium and indium terminated surfaces cut along the [001] direction. (a) angular-resolved photoemission spectroscopy plot along the high-symmetry path in proximity of the Fermi level (b) angular-resolved photoemission spectroscopy plot along the $W \to W$ direction. The touching point of the Weyl nodes from the bulk states is clearly visible, as well as the more pronounced bands related to the Fermi arcs that joins the two nodes. (c) Fermi surface of the surface states computed at $μ = - 0.096$ . The red (blue) dots represent the projection of the Weyl nodes with chirality $+ 1$ ( $- 1$ ). The Fermi arcs going from nodes of opposite chirality can be observed.
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Figure 6
Plot of the Berry curvature on a $k_{z} = 0$ plane in proximity of two neighboring WNs. The red and blue dots represent a node with chirality $+ 1$ and $- 1,$ respectively. While the 2D plot highlights only the in-plane components of the Berry curvature, the magnitude along the $z$ axis is also taken into account in order to give a more realistic picture when trying to infer the chirality of a node from the plot.
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Physical Review Research

Type-I antiferromagnetic Weyl semimetal InMnTi2

Davide Grassano, Luca Binci, and Nicola Marzari

Phys. Rev. Research 6, 013140 – Published 2 February 2024

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Type-I antiferromagnetic Weyl semimetal ${InMnTi}_{2}$