Hermann Freire

Field-theoretical renormalization group for a flat two-dimensional Fermi surface

We implement an explicit two-loop calculation of the coupling functions and the self-energy of interacting fermions with a two-dimensional flat Fermi surface in the framework of the field theoretical renormalization group (RG) approach. Throughout the calculation both the Fermi surface and the Fermi velocity are assumed to be fixed and unaffected by interactions. We show that in two dimensions, in a weak coupling regime, there is no significant change in the RG flow compared to the well-known one-loop results available in the literature. However, if we extrapolate the flow to a moderate coupling regime there are interesting new features associated with an anisotropic suppression of the quasiparticle weight

Strong competition between

Z

\Theta_{II}

along the Fermi surface, and the vanishing of the renormalized coupling functions for several choices of the external momenta.

-loop-current order and

We study the fate of the so-called

d

\Theta_{II}

-wave charge order along the diagonal direction in a two-dimensional hot spot model

-loop-current order that breaks both time-reversal and parity symmetries in a two-dimensional hot spot model with antiferromagnetically mediated interactions, using Fermi surfaces relevant to the phenomenology of the cuprate superconductors. We start from a three-band Emery model describing the hopping of holes in the CuO

Insulating spin liquid in the lightly doped two-dimensional Hubbard model

_{2}

Renormalization group calculation of the uniform susceptibilities in low-dimensional systems

plane that includes two hopping parameters

Coexistence of

t_{pp}

\Theta_{II}

and