Abstract
In this seminar, I will introduce the diagrammatic Monte Carlo method and discuss its application to the two-dimensional Hubbard model at finite temperature. The results obtained through this approach are controlled and, importantly, address the infinite-size limit of the model, thus yielding physical quantities with arbitrary momentum resolution. This enables a detailed investigation of the impact of electronic correlations on the spectral properties, with a particular focus on the Fermi surface topology and the pseudogap regime. We demonstrate the selective suppression of quasiparticle excitations near the antinodal regions due to the development of magnetic correlations, observed both in the weak coupling regime with a large correlation length and in the strong coupling regime with a shorter correlation length. Furthermore, I will discuss how a modified spin-fluctuation theory can account for these findings. Finally, the evolution of the pseudogap regime with decreasing temperature will be examined, revealing its instability and eventual transition into an ordered stripe phase, consistent with ground-state calculations.
