Fermi pockets and correlation effects in underdoped YBa2Cu3O6.5

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