High-performance channel-decomposed functional renormalization group scheme for fermions on 2d lattices

The truncated unity functional renormalization group (TUfRG) approach is a novel functional renormalization group (fRG) variant for interacting fermions. It is based on an exchange parametrization of the two-fermion interaction [1], while the structure of the equations and some more advantageous aspects are inspired by the singular-mode functional renormalization group put forward by Wang et al.[2]. On the basis of speedup data gained from our implementation we show that the TUfRG facilitates efficient calculations on a large number of multi-core CPUs. In this context, it will be illustrated that a separation of the underlying equations as done here is numerically advantageous. In order to discuss the virtues this method, we compare data for the 𝑡,𝑡′ Hubbard model on the square lattice to those from other fRG methods. Furthermore, we analyze the effects of including longer ranged interactions in addition to the purely local Hubbard interaction.