Experimental realization of type-II Weyl state in noncentrosymmetric ${\mathrm{TaIrTe}}_{4}$

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Experimental realization of type-II Weyl state in noncentrosymmetric ${TaIrTe}_{4}$

E. Haubold, K. Koepernik, D. Efremov, S. Khim, A. Fedorov, Y. Kushnirenko, J. van den Brink, S. Wurmehl, B. Büchner, T. K. Kim, M. Hoesch, K. Sumida, K. Taguchi, T. Yoshikawa, A. Kimura, T. Okuda, and S. V. Borisenko

Phys. Rev. B 95, 241108(R) – Published 12 June 2017

Abstract

We present experimental evidence for a type-II noncentrosymmetric Weyl state in ${TaIrTe}_{4}$ where it has been recently predicted theoretically. We find direct correspondence between angle-resolved photoemission spectroscopy data and calculated electronic structure both in the bulk and the surface, and clearly observe the exotic surface states which support the quasi-one-dimensional Fermi arcs connecting only four Weyl points. Remarkably, these electronic states are spin polarized in the direction along the arcs, thus highlighting ${TaIrTe}_{4}$ as an interesting type-II Weyl semimetal with a promising application potential.

Received 3 January 2017
Revised 6 March 2017

DOI:https://doi.org/10.1103/PhysRevB.95.241108

Physics Subject Headings (PhySH)

Fermi surface Spin polarization Topological materials Weyl fermions

Angle-resolved photoemission spectroscopy Spin-resolved photoemission spectroscopy

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

E. Haubold¹, K. Koepernik¹, D. Efremov¹, S. Khim^1,2, A. Fedorov^1,3, Y. Kushnirenko¹, J. van den Brink^1,4, S. Wurmehl^1,4, B. Büchner^1,4, T. K. Kim⁵, M. Hoesch⁵, K. Sumida⁶, K. Taguchi⁶, T. Yoshikawa⁶, A. Kimura⁶, T. Okuda⁷, and S. V. Borisenko¹

¹IFW Dresden, Helmholtzstraße 20, 01069 Dresden, Germany
²Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Straße 40, 01187 Dresden, Germany
³II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
⁴Department of Physics, TU Dresden, 01062 Dresden, Germany
⁵Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
⁶Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
⁷Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima 739-0046, Japan

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Vol. 95, Iss. 24 — 15 June 2017

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Figure 1
(a) Crystal structure of ${TaIrTe}_{4}$ . (b) Calculated 3D Fermi surface. (c) Projection to $k_{x} - k_{y}$ plane. (d) Projection to $k_{x} - k_{z}$ plane. ARPES Fermi surface maps taken using different photon energies: (e) 100 eV with the Brillouin zone shown as a dashed box, (f) 70 eV, and (g) 25 eV. (h) Photon energy dependent ARPES scan from 20 to 100 eV. The $k_{z}$ values have been calculated using a standard procedure with an inner potential of 15 eV. A color scale used in (e)–(h) is shown as an inset.
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Figure 2
(a) Band-structure calculations along $X - Γ - X$ . (b) ARPES measurements along $X - Γ - X$ . (c) Zoomed-in band structure along $X - Γ - X$ . (d) Zoomed-in band structure along $U - Z - U$ . (e) Calculated spectral function at $k_{y} = 0$ for the (001) surface. (f) Corresponding ARPES data taken at 99 eV photon energy. (g) Calculated spectral function at $k_{y} = 0$ for the $(00 \bar{1})$ surface.
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Figure 3
(a) ARPES Fermi surface map with the shaded areas of hole pockets for comparison with dHvA. The Arrows indicate the positions of the cuts shown in (b) ( $H$ ) and (c) ( $E$ ). (b) and (c) ARPES momentum-energy cuts at positions shown by $H$ and $E$ in (a) with corresponding Fermi-level MDC curves on top. (d) ARPES Fermi surface map taken using 25 eV photons and covering three BZs. (e) Calculated Fermi surface map for the (001) surface. (f) Calculated Fermi surface map for the $(00 \bar{1})$ surface. (g) ARPES momentum distribution at 25 meV below the Fermi level. (h) Calculated momentum distribution of the intensity at 75 meV binding energy for the (001) surface. (i) Calculated momentum distribution of the intensity at 75 meV binding energy for the $(00 \bar{1})$ surface.
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Figure 4
(a) Spectral function calculated for $k_{y} = 0.05 Å^{- 1}$ and (d) for $k_{y} = 0.16 Å^{- 1}$ . (b), (e) Corresponding ARPES data. Peaks in MDCs and dispersing features are shown by white arrows. (c), (f) Second derivatives of (b) and (e) highlighting the presence of topological surface states. (g) Second derivative of the Fermi surface map of the second BZ, similar to the one shown in Fig. 3. Arcs are clearly seen and are shown by the arrows. The dashed box approximately corresponds to the typical portion of the $k$ space probed by spin-resolved ARPES (SARPES). Weyl points are shown as red crosses and the positions of both cuts from (a)–(f) are indicated with dashed arrows. (h)–(j), (l)–(o) Spin-resolved ARPES measurements performed at the points of the $k$ space schematically indicated by arrows next to the surface vector in the insets. (k) Schematic summary of the SARPES results. The electronic states on the arcs are spin polarized, as shown by the arrows within the BZ boundaries.
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Physical Review B

covering condensed matter and materials physics

Experimental realization of type-II Weyl state in noncentrosymmetric ${TaIrTe}_{4}$

E. Haubold, K. Koepernik, D. Efremov, S. Khim, A. Fedorov, Y. Kushnirenko, J. van den Brink, S. Wurmehl, B. Büchner, T. K. Kim, M. Hoesch, K. Sumida, K. Taguchi, T. Yoshikawa, A. Kimura, T. Okuda, and S. V. Borisenko

Phys. Rev. B 95, 241108(R) – Published 12 June 2017

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Physical Review B

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Experimental realization of type-II Weyl state in noncentrosymmetric TaIrTe4

E. Haubold, K. Koepernik, D. Efremov, S. Khim, A. Fedorov, Y. Kushnirenko, J. van den Brink, S. Wurmehl, B. Büchner, T. K. Kim, M. Hoesch, K. Sumida, K. Taguchi, T. Yoshikawa, A. Kimura, T. Okuda, and S. V. Borisenko

Phys. Rev. B 95, 241108(R) – Published 12 June 2017

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Experimental realization of type-II Weyl state in noncentrosymmetric ${TaIrTe}_{4}$