Sáenz de Buruaga, Nadir SamosSantalla, Silvia N.Sierra, GermánRodríguez Laguna, Javier2024-05-202024-05-202021-05-152469-996910.1103/PhysRevB.101.205121https://hdl.handle.net/20.500.14468/12053The rainbow state denotes a set of valence bond states organized concentrically around the center of a spin 1/2 chain. It is the ground state of an inhomogeneous XX Hamiltonian and presents a maximal violation of the area law of entanglement entropy. Here, we add a tunable exchange coupling constant at the center, γ , and show that it induces entanglement transitions of the ground state. At very strong inhomogeneity, the rainbow state survives for 0≤γ≤1 , while outside that region the ground state is a product of dimers. In the weak inhomogeneity regime, the entanglement entropy satisfies a volume law, derived from CFT in curved space-time, with an effective central charge that depends on the inhomogeneity parameter and γ . In all regimes we have found that the entanglement properties are invariant under the transformation γ ⟷ 1 − γ , whose fixed point γ = 1 / 2 corresponds to the usual rainbow model. Finally, we study the robustness of nontrivial topological phases in the presence of the defect.eninfo:eu-repo/semantics/openAccessartículo