Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 43: Theory of electronic structure

HL 43.7: Talk

Thursday, March 29, 2007, 15:30–15:45, H14

The impact of self-consistency and vertex corrections in GW calculations. — •Maxim Shishkin and Georg Kresse — Institut fuer Materialphysik and Centre for Computational Materials Science, Universitaet Wien, A 1090 Wien, Austria

The GW method is a common choice for accurate calculations of electronic band structures in solids. The commonly used single shot GW approximation (G0W0) is plagued by reliance on DFT wavefunctions and energies, which do not always provide a reasonable input. As a remedy to this problem, we present here the results of self-consistent quasiparticle calculations (scGW) [1] with a full update of both eigenvalues and wavefunctions, performed using the VASP code. The obtained gaps are generally overestimated for most of the materials, which is however not surprising as the higher terms in the many body expansion of the Hamiltonian (vertex corrections) are missing. Indeed, it is shown that addition of vertex corrections decreases the gaps, bringing them into much closer agreement with experiment. We propose that the overestimation of scGW gaps can be caused by an inaccurate description of dielectric properties (underestimated static dielectric constants), resulting from neglect of electron-hole interaction in the calculation of polarizabilities and dielectric matrices. The vertex correction contributions, which includes such electron-hole interactions, lead to an increase of dielectric constants to values close to experiment, and a concomitant decrease of the gaps.

[1] M. van Schilfgaarde, T. Kotani, and S. Faleev, Phys. Rev. Lett., vol. 96, 226402 (2006).