Theory of Fermi-surface pockets and correlation effects in underdoped YBa2Cu3O6.5

The detection of quantum oscillations in the electrical resistivity of YBa2Cu3O6.5 provides evidence for the existence of Fermi-surface pockets in an underdoped cuprate. We present a theoretical study of the electronic structure of YBa2Cu3O7 (-) (delta) aimed at establishing the nature of these pockets-i.e., CuO2 plane vs CuO chain or BaO. We argue that electron correlation effects, such as orbital-dependent band distortions and anisotropic self-energy corrections, must be taken into account to interpret the quantum oscillation experiments.