Quasiparticle band structures of PbS, PbSe and PbTe including pressure effects

The electronic quasiparticle energies of PbS, PbSe and PbTe are calculated with the quasiparticle self-consistent GW approximation (QSGW, van Schilfgaarde, Kotani and Faleev) including spin-orbit coupling. The semiconducting gap is formed between states of L$_{6}$ symmetry (L$_{6}^{+}$ and L$_{6}^{-})$, which is the reason why these materials are semiconductors even in the local-density approximation (LDA) due to band repulsion. Closer inspection reveals that in PbS and PbSe the order of the L$_{6}$ states is reversed in the LDA compared to the QSGW bands. This leads to the wrong sign of the band gap deformation potentials for PbS and PbSe in the LDA. With QSGW both sign and magnitude of the deformation potentials are in agreement with experiments. Also, results obtained for effective masses and band gaps as functions of pressure will be discussed.