Fig. 4: Causal structures with quantum horizon region.
From: Causal structure of interacting Weyl fermions in condensed matter systems
a–c Band structure as a function of kx with A = 0.3, θ = 1, k1 = 1.1π/2, ky = 0, and kz = π/2. a Without CDW, the Fermi velocities of the two Weyl quasiparticles are different. b Without CDW (δ = 0), the folded bands in the double supercell BZ along the x-direction. The Weyl node I is in the energy-like region of Weyl node II but Weyl node II is in the momentum-like region of Weyl node I. c With CDW of Q-vector along (π, 0, 0) and the CDW strength δ = 0.05: The Weyl nodes remain intact and there is no metal-insulator phase transition. d The causal structure of a correlated Weyl system. The quantum horizon region is shown as a “thick horizon” bounded by the Fermi velocities VF,H and VF,L of the two interacting fermions.
