Fermiology of cuprates from first principles: From small pockets to the Luttinger Fermi surface

Fermiology, the shape and size of the Fermi surface, underpins the low-temperature physical properties of a metal. Recent investigations of the Fermi surface of high-Tc superconductors, however, show a most unusual behavior: upon addition of carriers, ``Fermi'' pockets appear around nodal (hole doping) and antinodal (electron doping) regions of the Brillouin zone in the ``pseudogap'' state. With progressive doping, δ, these evolve into well-defined Fermi surfaces around optimal doping (δₒₚₜ), with no pseudogap. Correspondingly, various physical responses, including d-wave superconductivity, evolve from highly anomalous up to δₒₚₜ, to more conventional beyond. Describing this evolution holds the key to understanding high-temperature superconductivity. Here, we present ab initio quantum chemical results for cuprates, in an attempt to provide a quantitative description of the evolution of the Fermi surface with δ. Our results constitute an ab initio justification for several hitherto proposed semiphenomenological theories, offering a unified basis for understanding of various unusual physical responses of cuprates.