Ideal Weyl semimetal states with point Fermi surfaces in Cu₂SnSe₃series compounds

In most Weyl semimetals (WSMs), the Weyl nodes lie away from the Fermi energy and their Weyl cones are often obscured by the extended Fermi surfaces, suppressing hallmark Weyl phenomena. Here, we propose a mechanism for realizing ideal WSMs: a class of semiconductors can undergo a transition into ideal WSM via bandgap closing. This transition can be driven by chemical doping, which modulates the band gap and enhances spin-orbit coupling, leading to linear crossing between the valence and conduction bands and triggering the topological phase transition. Using first-principles calculations, we demonstrate the realization of this mechanism in the Cu2SnSe3series materials, where two pairs of Weyl points emerge extremely close to the Fermi level. The Fermi surface becomes point-like, while the surface states exhibit well-defined Fermi arcs, representing an ideal WSM. This mechanism offers an ideal platform for exploring ideal topological states and anomalous transport phenomena in WSMs.