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In some d-electron oxides the measured effective mass m(exptl) has long beenknown to be significantly larger than the model effective mass m(model) deducedfrom mean-field band theory, i.e., m(exptl) = beta * m(model), where beta > 1is the "mass enhancement", or "mass renormalization" factor. Previousapplications of density functional theory (DFT), based on the smallest numberof possible magnetic, orbital, and structural degrees of freedom, missed suchmass enhancement, a fact that was taken as evidence of strong electroniccorrelation being the exclusive enabling physics. The current paper reportsthat known modalities of energy-lowering symmetry-broken spin and structuraleffects included in mean-field DFT show mass enhancement for both electrons andholes in a range of d-electron perovskites SrVO3, SrTiO3, BaTiO3, and LaMnO3 aswell as p-electron perovskites CsPbI3 and SrBiO3, including metals (SrVO3) andinsulators (the rest). This is revealed only when enlarged unit cells of thesame parent global symmetry, which are large enough to allow for symmetrybreaking distortions and concomitant variations in spin order, are explored fortheir ability to lower the total energy. The paper analyzes the contributionsof different symmetry-broken modalities to mass enhancement, finds commoneffects in the range of d- as well as p-electron perovskites. Thus, symmetrybreaking in mean-field theory could describe effects that were previouslyattributed exclusively to complex correlated treatments. Indeed, brokensymmetries are often experimentally observed, e.g., octahedral tilting,Jahn-Teller distortions, or bond disproportionation, and often provideintuitive explanations in terms of degeneracy removal due to lowering ofstructural symmetry, or as shifting of band energies in explainable directions.

Mass enhancement in 3d and s-p perovskites from symmetry breaking