Global quantum discord (GQD) in two‐dimensional (2D) transverse‐field Ising models on N × N square lattices at zero temperature and finite temperatures are studied. First, the GQD G(ρ2×2) defined on the reduced density matrix ρ2×2 of a 2 × 2 sub‐square in the center of the N × N lattices, with N=4, 5, 6, 7, ∞ is studied. It is found that G(ρ2×2) shows little size dependence in the strong‐field and weak‐field limit, and presents dramatic size dependence in the middle‐field region. The results are explained by short‐ran...
