Fig. 10: Frozen phonon bandstructure.

PBE+G0W0 calculation using the mean-squared displacement at T = 0 K along different phonon eigenvectors in both positive and negative direction. The bandstructure couples strongly to the B2g phonon modes II and IV at 2 and 3.4 THz, which exhibit the characteristic shearing of the Ta atoms. The figure has been adapted from our work in ref. 28.