Wave-function-based approach to quasiparticle bands: new insight into the electronic structure of c-ZnS

TL;DR

This paper employs wave-function-based ab initio methods to accurately describe quasiparticle energy bands in zinc-blende ZnS, especially focusing on the Zn 3d semicore states, surpassing the limitations of LDA and GW approximations.

Contribution

It introduces a local Hamiltonian approach using localized Wannier functions to improve the description of Zn 3d states in ZnS, accounting for short-range and long-range electron correlation effects.

Findings

Zn 3d states are about 9.0 eV below the valence band top.

The method yields results in very good agreement with experimental photoemission data.

Corrections to Hartree-Fock energies and gaps are several eV, with long-range polarization around 1.0 eV.

Abstract

Ab initio wave-function-based methods are employed for the study of quasiparticle energy bands of zinc-blende ZnS, with focus on the Zn 3d "semicore" states. The relative energies of these states with respect to the top of the S 3p valence bands appear to be poorly described as compared to experimental values not only within the local density approximation (LDA), but also when many-body corrections within the GW approximation are applied to the LDA or LDA+U mean-field solutions [T. Miyake, P. Zhang, M. L. Cohen, and S. G. Louie, Phys. Rev. B 74, 245213 (2006)]. In the present study, we show that for the accurate description of the Zn 3d states a correlation treatment based on wave function methods is needed. Our study rests on a local Hamiltonian approach which rigorously describes the short-range polarization and charge redistribution effects around an extra hole or electron placed into the valence respective conduction bands of semiconductors and insulators. The method also facilitates the computation of electron correlation effects beyond relaxation and polarization. The electron correlation treatment is performed on finite clusters cut off the infinite system. The formalism makes use of localized Wannier functions and embedding potentials derived explicitly from prior periodic Hartree-Fock calculations. The on-site and nearest-neighbor charge relaxation lead to corrections of several eV to the Hartree-Fock band energies and gap. Corrections due to long-range polarization are of the order of 1.0 eV. The dispersion of the Hartree-Fock bands is only little affected by electron correlations. We find the Zn 3d "semicore" states to lie about 9.0 eV below the top of the S 3p valence bands, in very good agreement with values from valence-band x-ray photoemission.