Charge expulsion, charge inhomogeneity and phase separation in dynamic Hubbard models

TL;DR

Dynamic Hubbard models, which incorporate orbital expansion effects, tend to expel negative charge and develop inhomogeneity and phase separation, potentially explaining observed phenomena in cuprate oxides.

Contribution

This paper demonstrates that dynamic Hubbard models naturally lead to charge expulsion and inhomogeneity, offering a new explanation for experimental observations in complex materials.

Findings

Charge expulsion from interior to surface in dynamic Hubbard models

Development of charge inhomogeneity and phase separation

Potential explanation for charge phenomena in cuprate oxides

Abstract

Dynamic Hubbard models are extensions of the conventional Hubbard model that take into account the fact that atomic orbitals expand upon double occupancy. It is shown here that systems described by dynamic Hubbard models have a tendency to expel negative charge from their interior to the surface, and to develop charge inhomogeneity and even phase separation in the bulk. These effects are associated with lowering of electronic kinetic energy. We propose that these models may explain the charge inhomogeneity and negatively charged grain boundaries observed in cuprate oxides and other materials.