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Two-Dimensional Folding Technique For Enhancing Fermi Surface Signatures In The Momentum Density: Application To Compton Scattering Data From An Al-3 At. % Li Disordered Alloy, I. Matsumoto, J. Kwiatkowska, F. Maniawski, M. Itou, H. Kawata, N. Shiotani, S. Kaprzyk, P. E. Mijnarends, B. Barbiellini, A. Bansil
Two-Dimensional Folding Technique For Enhancing Fermi Surface Signatures In The Momentum Density: Application To Compton Scattering Data From An Al-3 At. % Li Disordered Alloy, I. Matsumoto, J. Kwiatkowska, F. Maniawski, M. Itou, H. Kawata, N. Shiotani, S. Kaprzyk, P. E. Mijnarends, B. Barbiellini, A. Bansil
Bernardo Barbiellini
We present a technique for enhancing Fermi surface (FS) signatures in the two-dimensional (2D) distribution obtained after the 3D momentum density in a crystal is projected along a specific direction in momentum space. These results are usEFul for investigating fermiology via high-resolution Compton scattering and positron annihilation spectroscopies. We focus on the particular case of the (110) projection in a fcc crystal where the standard approach based on the use of the Lock-Crisp-West (LCW) folding theorem fails to give a clear FS image due to the strong overlap with FS images obtained through projection from higher Brillouin zones. We show …
Role Of Oxygen Electrons In The Metal-Insulator Transition In The Magnetoresistive Oxide La2-2xsr1+2xmn2o7 Probed By Compton Scattering, B. Barbiellini, A. Koizumi, P. E. Mijnarends, W. Al-Sawai, Hsin Lin, T. Nagao, K. Hirota, M. Itou, Y. Sakurai, A. Bansil
Role Of Oxygen Electrons In The Metal-Insulator Transition In The Magnetoresistive Oxide La2-2xsr1+2xmn2o7 Probed By Compton Scattering, B. Barbiellini, A. Koizumi, P. E. Mijnarends, W. Al-Sawai, Hsin Lin, T. Nagao, K. Hirota, M. Itou, Y. Sakurai, A. Bansil
Bernardo Barbiellini
We have studied the [100]-[110] anisotropy of the Compton profile in the bilayer manganite. Quantitative agreement is found between theory and experiment with respect to the anisotropy in the two metallic phases (i.e., the low temperature ferromagnetic and the colossal magnetoresistant phase under a magnetic field of 7 T). Robust signatures of the metal-insulator transition are identified in the momentum density for the paramagnetic phase above the Curie temperature. We interpret our results as providing direct evidence for the transition from the metalliclike to the admixed ionic-covalent bonding accompanying the magnetic transition. The number of electrons involved in this phase …
Resonating-Valence-Bond Ground State Of Lithium Nanoclusters, D. Nissenbaum, L. Spanu, C. Attaccalite, B. Barbiellini, A. Bansil
Resonating-Valence-Bond Ground State Of Lithium Nanoclusters, D. Nissenbaum, L. Spanu, C. Attaccalite, B. Barbiellini, A. Bansil
Bernardo Barbiellini
We have performed diffusion quantum Monte Carlo simulations of Li clusters showing that resonating-valence-bond (RVB) pairing correlations between electrons provide a substantial contribution to the cohesive energy. The RVB effects are identified in terms of electron transfers from s-like to p-like character, constituting a possible explanation for the breakdown of the Fermi-liquid picture observed in recent high-resolution Compton scattering experiments for bulk Li.
Fermi-Surface Study Of Ba₁₋ₓkₓbio₃, S. Sahrakorpi, B. Barbiellini, R. Markiewicz, S. Kaprzyk, M. Lindroos, A. Bansil
Fermi-Surface Study Of Ba₁₋ₓkₓbio₃, S. Sahrakorpi, B. Barbiellini, R. Markiewicz, S. Kaprzyk, M. Lindroos, A. Bansil
Bernardo Barbiellini
We present all-electron computations of the three-dimensional (3D) Fermi surfaces (FS’s) in Ba₁₋ₓKₓBiO₃ for a number of different compositions based on the self-consistent Korringa-Kohn-Rostoker coherent-potential-approximation approach for incorporating the effects of Ba/K substitution. By assuming a simple cubic structure throughout the composition range, the evolution of the nesting and other features of the FS of the underlying pristine phase is correlated with the onset of various structural transitions with K doping. A parametrized scheme for obtaining an accurate 3D map of the FS in Ba₁₋ₓKₓBiO₃ for an arbitrary doping level is developed. We remark on the puzzling differences between the …
Dyson Orbitals, Quasi-Particle Effects And Compton Scattering, B. Barbiellini, A. Bansil
Dyson Orbitals, Quasi-Particle Effects And Compton Scattering, B. Barbiellini, A. Bansil
Bernardo Barbiellini
Dyson orbitals play an important role in understanding quasi-particle effects in the correlated ground state of a many-particle system and are relevant for describing the Compton scattering cross section beyond the frameworks of the impulse approximation (IA) and the independent particle model (IPM). Here we discuss corrections to the Kohn-Sham energies due to quasi-particle effects in terms of Dyson orbitals and obtain a relatively simple local form of the exchange-correlation energy. Illustrative examples are presented to show the usefulness of our scheme.
Compton Scattering Beyond The Impulse Approximation, I. G. Kaplan, B. Barbiellini, A. Bansil
Compton Scattering Beyond The Impulse Approximation, I. G. Kaplan, B. Barbiellini, A. Bansil
Bernardo Barbiellini
We treat the non-relativistic Compton scattering process in which an incoming photon scatters from an N-electron many-body state to yield an outgoing photon and a recoil electron, without invoking the commonly used frameworks of either the impulse approximation (IA) or the independent particle model (IPM). An expression for the associated triple differential scattering cross section is obtained in terms of Dyson orbitals, which give the overlap amplitudes between the N-electron initial state and the (N-1) electron singly ionized quantum states of the target. We show how in the high energy transfer regime, one can recover from our general formalism the …