High-Entropy Engineering of the Crystal and Electronic Structures in a Dirac Material

General approaches for realizing new Dirac/Weyl states employ computational assistance, external perturbation, or chemical substitution. Of these, the chemical substitution method has been proven to be effective in tuning lattice distortions and spin-orbital coupling and thus controlling the topological phase. However, an accessible range of lattice distortion in a substituted system just follows Vegard’s law and rarely goes beyond distortions of the end members. In addition, the emergence of a new symmetry structure can hardly be expected especially when the end members are isosymmetric. In this talk, we show a widely applicable strategy that uses high configuration entropy for manipulating relativistic electronic states, which overcomes the limitations of the conventional solid-solution approach. We take the AMnSb₂ (A = Ba, Sr, Ca, Eu, and Yb) Dirac material family as an example and demonstrate that mixing of the five A cations gives access to a polar P2₁mn structure, which is not present in any of the parent compounds. The high-entropy phase preserves the linear dispersion despite the severe lattice disorder. Our Shubnikov–de Haas oscillations measurements reveal that the Dirac state, which is 2D in the parent AMnSb₂, evolves into quasi-3D in the high-entropy phase. Our first-principles calculation suggests that such a morphology evolution of the relativistic state is triggered by local rumpling distortion of Sb atoms originating from disordered coordination due to the high-entropy A layers.