Vertex corrections inclusions in the improved two-particle self-consistent approach for optical conductivity calculations

Transport properties, such as the optical conductivity and the Seebeck effect prove to be challenging to compute in strongly correlated materials. One important model to study such materials is the Hubbard model. A useful method to find approximate solutions for electron doped cuprates is the Two-Particle Self-Consistent approach (TPSC) [1]. Previous work has used this method including vertex corrections to compute DC and optical conductivity [2]. These calculations however, are very tedious.

In this work, we use the Improved Two-Particle Self-Consistent approach (TPSC+) [3] to compute said transport properties with the goal to obtain results including vertex corrections much more efficiently and to benchmark this recent approach. We show that TPSC+ mostly includes Maki-Thompson-like and Aslamsov-Larkin-like vertex corrections at electron doping above 0.2 at high temperatures with only small deviations from the f-sum rule.