Lucia Reining

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We have measured a strictly linear pi plasmon dispersion along the axis of individualized single-wall carbon nanotubes, which is completely different from plasmon dispersions of graphite or bundled single-wall carbon nanotubes. Comparative ab initio studies on graphene-based systems allow us to reproduce the different dispersions. This suggests that(More)
Starting from the many-body Bethe-Salpeter equation we derive an exchange-correlation kernel f(xc) that reproduces excitonic effects in bulk materials within time-dependent density functional theory. The resulting f(xc) accounts for both self-energy corrections and the electron-hole interaction. It is static, nonlocal, and has a long-range Coulomb tail.(More)
Time-dependent density-functional theory (TDDFT) is widely used in the study of linear response properties of finite systems. However, there are difficulties in properly describing excited states, which have double- and higher-excitation characters, which are particularly important in molecules with an open-shell ground state. These states would be(More)
We present an ab initio numerical many-body GW calculation of the band plot in freestanding graphene. We consider the full ionic and electronic structure introducing e-e interaction and correlation effects via a self-energy containing non-Hermitian and dynamical terms. With respect to the density-functional theory local-density approximation, the Fermi(More)
We have established and implemented a fully ab initio method which allows one to calculate optical absorption spectra, including excitonic effects, without solving the cumbersome Bethe-Salpeter equation, but obtaining results of the same precision. This breakthrough has been achieved in the framework of time-dependent density-functional theory, using new(More)
State-of-the-art theoretical methods fail in describing the optical absorption spectrum, band gap, and optical onset of Cu(2)O. We have extended a recently proposed self-consistent quasiparticle approach, based on the GW approximation, to the calculation of optical spectra, including excitonic effects. The band structure compares favorably with our present(More)
Vanadium dioxide is a prototype material for the discussion of correlation effects in solids. First-principles density-functional theory does not describe the metal-insulator transition, whereas strongly correlated models reproduce the main features. Here we present a parameter-free GW calculation of VO2 and show that the correlation effects in the band(More)
We propose an alternative formulation of many-body perturbation theory that uses the density-functional concept. Instead of the usual four-point integral equation for the polarizability, we obtain a two-point one, which leads to excellent optical absorption and energy-loss spectra. The corresponding three-point vertex function and self-energy are then(More)
It is commonly accepted that the GW approximation for the electron self-energy is successful for the description of the band structure of weakly to moderately correlated systems, whereas it will fail for strongly correlated materials. In the present work, we discuss two important aspects of this approximation: first, the "self-screening error," which is due(More)