Effective spin-orbital model for correlated 2DEGs in (111) oxide heterostructures

Recent experiments have begun exploring the physics of 2D electron gases in (111) oxide heterostructures. Motivated by understanding the nature of broken symmetry states which could be potentially realized in such 2DEGs, we have studied correlation effects and the impact of thermal fluctuations by studying an effective spin-orbital Hamiltonian. The form of the Hamiltonian is dictated by symmetry and its parameters are obtained by a detailed comparison with a Hartree-Fock mean field theory. A Monte Carlo study of this effective model shows that the system transitions from a high temperature paramagnetic phase into a low temperature nematic phase with ferro-orbital order. We discuss such ordering tendencies in light of recent experiments on such (111) 2DEGs which appear to find broken rotational symmetry.