Description
A significant part of the phase diagram of the 2D fermionic
Hubbard model in the non-perturbative regime of moderate
interactions and filling factors (U<4,n<0.7) is governed by
effective Fermi liquid physics with emergent weak BCS-type
instabilities. I will discuss how the bold-line diagrammatic
Monte Carlo technique with semi-analytic treatment of the
Cooper instability can be used to address this system without
uncontrolled approximations. I will present an accurate
ground-state phase diagram in the (n,U) plane, describing
competition between the p- and d-wave superfluid states.
However, critical temperatures prove to be small in this
regime at least up to U=4, n=0.6, where skeleton expansions
for the Hubbard model break down and the bare series
diverges. I will introduce a method for controlling the
convergence radius of bare diagrammatic expansions, which
allows us to investigate in a controllable manner the
pseudogap regime of the Hubbard model and to study the
nodal/antinodal dichotomy at low doping and values of
coupling inaccessible before.
