Closing the gaps in our understanding of the pseudogap*

In this talk, I will review recent theoretical progress in understanding the pseudogap phenomenon in the two-dimensional Hubbard model, in relation to hole-doped cuprate superconductors. I will show that two independent computational methods (cluster extensions of dynamical mean-field theory, and lattice diagrammatic Monte Carlo) yield quantitatively consistent results. These two methods indicate that short-range antiferromagnetic correlations are responsible for the opening of the pseudogap in the strong-coupling regime. The Fermi surface is strongly modified by interactions, and a pseudogap only opens when this surface is hole-like. For small to moderate ratios of t’/t, the collapse of the pseudogap is found to coincide with the Lifshitz transition of the Fermi surface from hole-like to electron-like, in agreement with experimental observations. These findings can be rationalized within an SU(2) gauge theory of a metal with short-range fluctuating antiferromagnetic order, in which topological order is responsible for the reconstruction of the Fermi surface into pockets.

References: Wei Wu et al. Phys Rev B 96, 041105R (2017); arXiv:1707.06602. M.Scheurer et al., in preparation.