3 research outputs found
Maximally localized Wannier functions in LaMnO3 within PBE+U, hybrid functionals, and partially self-consistent GW: an efficient route to construct ab-initio tight-binding parameters for e_g perovskites
Using the newly developed VASP2WANNIER90 interface we have constructed
maximally localized Wannier functions (MLWFs) for the e_g states of the
prototypical Jahn-Teller magnetic perovskite LaMnO3 at different levels of
approximation for the exchange-correlation kernel. These include conventional
density functional theory (DFT) with and without additional on-site Hubbard U
term, hybrid-DFT, and partially self-consistent GW. By suitably mapping the
MLWFs onto an effective e_g tight-binding (TB) Hamiltonian we have computed a
complete set of TB parameters which should serve as guidance for more elaborate
treatments of correlation effects in effective Hamiltonian-based approaches.
The method-dependent changes of the calculated TB parameters and their
interplay with the electron-electron (el-el) interaction term are discussed and
interpreted. We discuss two alternative model parameterizations: one in which
the effects of the el-el interaction are implicitly incorporated in the
otherwise "noninteracting" TB parameters, and a second where we include an
explicit mean-field el-el interaction term in the TB Hamiltonian. Both models
yield a set of tabulated TB parameters which provide the band dispersion in
excellent agreement with the underlying ab initio and MLWF bands.Comment: 30 pages, 7 figure
Unconventional pairing originating from disconnected Fermi surfaces in the iron-based superconductor
For the iron-based high superconductor LaFeAsOF, we
construct a minimal model, where all of the five Fe bands turn out to be
involved. We then investigate the origin of superconductivity with a five-band
random-phase approximation by solving the Eliashberg equation. We conclude that
the spin fluctuation modes arising from the nesting between the disconnected
Fermi pockets realise, basically, an extended s-wave pairing, where the gap
changes sign across the nesting vector.Comment: 17pages, 4 figures, to be published in Physica C, Special Edition on
Superconducting Pnictides, contains corrections to our previous paper PRL
101, 087004 (2008
Spin Channels in Functionalized Graphene Nanoribbons
We characterize the transport properties of functionalized graphene
nanoribbons using extensive first-principles calculations based on density
functional theory (DFT) that encompass both monovalent and divalent ligands,
hydrogenated defects and vacancies. We find that the edge metallic states are
preserved under a variety of chemical environments, while bulk conducting
channels can be easily destroyed by either hydrogenation or ion or electron
beams, resulting in devices that can exhibit spin conductance polarization
close to unity.Comment: 14 pages, 5 figure