Hubbard Physics in the PAW GW Approximation

TL;DR

This paper demonstrates how modifying screening in PAW GW calculations can simulate Hubbard physics, capturing Mott insulator behavior and differentiating between insulating phases in vanadium dioxide.

Contribution

It introduces a method to incorporate Hubbard physics into GW calculations by adjusting screening, enabling the simulation of Mott insulators without significant nesting.

Findings

Successfully opens Mott gap in CuO with spectral weight transfer

Distinguishes M1 and M2 VO2 as Peierls insulator and Mott insulator respectively

Standard GW suffices for M1 VO2 gap, but M2 requires strong correlations

Abstract

It is demonstrated that the signatures of the Hubbard Model in the strongly interacting regime can be simulated by modifying the screening in the limit of zero wavevector in Projector-Augmented Wave GW calculations for systems without significant nesting. This modification, when applied to the Mott insulator CuO, results in the opening of the Mott gap by the splitting of states at the Fermi level into upper and lower Hubbard bands, and exhibits a giant transfer of spectral weight upon electron doping. The method is also employed to clearly illustrate that the M$_{1}$ and M$_{2}$ forms of vanadium dioxide are fundamentally different types of insulator. Standard GW calculations are sufficient to open a gap in M$_{1}$ VO$_{2}$, which arise from the Peierls pairings filling the valence band, creating homopolar bonds. The valence band wavefunctions are stabilized with respect to the conduction band, reducing polarizability and pushing the conduction band eigenvalues to higher energy. The M$_{2}$ structure however opens a gap from strong on-site interactions; it is a Mott insulator.