I am currently working with graphene 2D approach, and I am wondering how is computed the interband term. From the kubo formula, it is possible to solve the intraband term analytically, that is fine. However, I don’t find any details on the interband term. It comes from the second part of the kubo formula, where the integral is non solvable analytically. Could you give me clue on the way lumerical compute this interband conductivity term ?