Synthesis of a semimetallic Weyl ferromagnet, (Cr,Bi)₂Te₃

Quantum materials governed by emergent topological fermions have become a cornerstone of physics. However, there are few materials whose electromagnetic response is dominated by emergent Weyl fermions. Nearly all known Weyl materials are overwhelmingly metallic, and are largely governed by irrelevant, conventional electrons [1-4]. Here we theoretically predict and experimentally observe a semimetallic Weyl ferromagnet in (Cr,Bi)₂Te₃ [5]. In transport, we find a record bulk anomalous Hall angle > 0.5 along with non-metallic conductivity, a regime sharply distinct from conventional ferromagnets and known Weyl materials. Together with symmetry analysis, our data suggest a semimetallic Fermi surface composed of two Weyl points, with a giant separation > 75% of the linear dimension of the bulk Brillouin zone, and no other electronic states. Using state-of-the-art molecular beam epitaxy, we widely tune the electronic structure, allowing us to annihilate the Weyl state and visualize a Murakami-like topological phase diagram. Our semimetallic Weyl ferromagnet provides a unique platform for Weyl superconductors, Weyl thermoelectrics and neuromorphic computing [6].

[1] Hasan, Chang, Belopolski et al., Nat. Rev. Mat. 6, 784 (2021).

[2] Belopolski et al., Nature 604, 647 (2022).

[3] Belopolski et al., Science 365, 1278 (2019).

[4] Tokura, Yasuda and Tsukazaki, Nat. Rev. Phys. 1, 126 (2019).

[5] Belopolski et al., Nature, in press.

[6] Sato, Nagahama, Belopolski et al., Phys. Rev. Mat. 8, L041801 (2024).