Role of c-axis pairs in V2O3 from the band-structure point of view

The common interpretation of the LDA band structure of V$_{2}$O$_{3}$ is that the apparent splitting of the $a_{1g}$ band into a low intensity structure deep below the Fermi energy and a high intensity feature above it, is due to the bonding-antibonding coupling of the vertical V-V pair. Using tight-binding fitting to --as well as first-principles NMTO downfolding of-- the spin-up LDA+U $a_{1g}$ band, we show that there are other hopping integrals which are equally important for the band shape as the integral for hopping between the partners of the pair

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.Comment: A high-resolution version can be found at http://www.physics.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Articles/YBCO_OrthoII_LDA.pd