High-entropy engineering of the crystal and electronic structures in a Dirac material

Dirac and Weyl semimetals are a central topic of contemporary condensed matter physics, and the discovery of new compounds with Dirac/Weyl electronic states is crucial to the advancement of topological materials and quantum technologies. Here we show a widely applicable strategy that uses high configuration entropy to engineer relativistic electronic states. We take the AMnSb₂ (A = Ba, Sr, Ca, Eu, and Yb) Dirac material family as an example and demonstrate that mixing of Ba, Sr, Ca, Eu and Yb at the A site generates the compound (Ba_0.38Sr_0.14Ca_0.16Eu_0.16Yb_0.16)MnSb₂ (denoted as A⁵MnSb₂), giving access to a polar structure with a space group that is not present in any of the parent compounds. A⁵MnSb₂ is an entropy-stabilized phase that preserves its linear band dispersion despite considerable lattice disorder. Although both A⁵MnSb₂ and AMnSb₂ have quasi-two-dimensional crystal structures, the two-dimensional Dirac states in the pristine AMnSb₂ evolve into a highly anisotropic quasi-three-dimensional Dirac state triggered by local structure distortions in the high-entropy phase, which is revealed by Shubnikov–de Haas oscillations measurements.