Unveiling the nature of three dimensional orbital ordering transitions: the case of eg and t₂g models on the cubic lattice

الأصل · EN

We perform large scale finite-temperature Monte Carlo simulations of the classical eg and t₂g orbital models on the simple cubic lattice in three dimensions. The eg model displays a continuous phase transition to an orbitally ordered phase. While the correlation length exponent ν≈0.66(1) is close to the 3D XY value, the exponent η≈ 0.15(1) differs substantially from O(N) values. At Tc a U(1) symmetry emerges, which persists for T<Tc below a crossover length scaling as Λ ξᵃ, with an unusually small a≈1.3. Finally, for the t₂g model we find a first order transition into a low-temperature lattice-nematic phase without orbital order.