Site-occupation embedding theory(SOET) is an alternative formulation of density-functional theory (DFT) for lattice Hamiltonians where the physical problem is mapped onto an auxiliary impurity-interacting system rather than a non-interacting Kohn-Sham one. In this theory, the Coulomb repulsion is switched on in a smaller part of the lattice (impurity) and suppressed in the remaining part (bath). In previous works on SOET, the impurity problem has been solved self-consistently either exactly (for small rings) or at the density matrix renormalization group (DMRG) level for larger rings. The Coulomb repulsion in the bath is incorporated into an effective density-functional embedding potential which aims at restoring the density (i.e. the occupation of the sites) of the physical Hubbard model. In this work, we propose a new approach where we exploit the fact that there is a one-to-one correspondence (through the ground-state wave function) between the self-energy and the electron density. In consequence, the many-body impurity-interacting wave function in SOET is replaced by a Green function. Here, the associated impurity-interacting self-energy explicitly depends on the site occupation and is used to calculate the Green’s function which restores the correct site occupation of the physical Hubbard model. As a proof of concept, we will construct an approximate density-functional self-energy in this context from the two-electron asymmetric Anderson dimer.

Density-functional self-energy approach to site-occupation embedding theory

2019 Spring National Meeting

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