Michel Ferrero

In this seminar, I will present recent results on the fermionic Hubbard
model, a prototypical model for correlated quantum systems. The model is
at the same time very fundamental, playing a role similar to the Ising
model in classical statistical physics, but is also believed to be
relevant to the physics of certain strongly correlated materials, such as
cuprate superconductors. We use a diagrammatic Monte Carlo approach, a
method based on perturbation theory, which is able to obtain controlled
solutions for infinite lattice size at finite temperature. This allows for
a careful investigation of the consequences of electronic correlations on
the spectral properties, with an emphasis on the Fermi surface topology
and the pseudogap regime. I will discuss how quasiparticle excitations are
selectively destroyed near the antinodal regions because of the onset of
magnetic correlations, both at weak coupling when the correlation length
is large, and at strong coupling when it is shorter. Finally, I will
address the the fate of the pseudogap regime as temperature is lowered and
show that it is unstable and eventually turns into an ordered stripe
phase, as found by ground-state methods.