GWΓ + Bethe-Salpeter equation approach for photoabsorption spectra: Importance of self-consistent GWΓ calculations in small atomic systems

Riichi Kuwahara, Yoshifumi Noguchi, Kaoru Ohno

The self-consistent GWΓ method satisfies the Ward-Takahashi identity (i.e., the gauge invariance or the local charge continuity) for arbitrary energy ($\omega$) and momentum ($\mathbf{q}$) t…