Browsing by Author "Radonjić, Miloš M."

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    DFT+SIGMA2 method for electron correlation effects at transition metal surfaces
    Droghetti, Andrea; Radonjić, Miloš M.; Halder, Anita; Rungger, Ivan; Chioncel, Liviu
    We present a computational approach for electronically correlated metallic surfaces and interfaces, which combines density functional and dynamical mean-field theory using a multiorbital perturbative solver for the many-body problem. Our implementation is designed to describe ferromagnetic metallic thin films on a substrate. The performances are assessed in detail for a Fe monolayer on a W(110) substrate, a prototypical nanoscale magnetic system. Comparing our results to photoemission data, we find qualitative and quantitative improvements in the calculated spectral function with respect to the results of density functional theory within the local spin density approximation. In particular, the spin splitting of the d states is drastically reduced and, at the same time, their spectral width becomes narrower. The method is, therefore, able to account for the main correlation effects in the system.
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    Enhancing Electron Correlation at a 3d Ferromagnetic Surface
    Janas, David, Maximilian; Droghetti, Andrea; Ponzoni, Stefano; Cojocariu, Iulia; Jugovac, Matteo; Vitaliy Feyer; Radonjić, Miloš M.; Rungger, Ivan; Chioncel, Liviu; Zamborlini, Giovanni; Cinchetti, Mirko
    Spin-resolved momentum microscopy and theoretical calculations are combined beyond the one-electron approximation to unveil the spin-dependent electronic structure of the interface formed between iron (Fe) and an ordered oxygen (O) atomic layer, and an adsorbate-induced enhancement of electronic correlations is found. It is demonstrated that this enhancement is responsible for a drastic narrowing of the Fe d-bands close to the Fermi energy (E-F) and a reduction of the exchange splitting, which is not accounted for in the Stoner picture of ferromagnetism. In addition, correlation leads to a significant spin-dependent broadening of the electronic bands at higher binding energies and their merging with satellite features, which are manifestations of a pure many-electron behavior. Overall, adatom adsorption can be used to vary the material parameters of transition metal surfaces to access different intermediate electronic correlated regimes, which will otherwise not be accessible. The results show that the concepts developed to understand the physics and chemistry of adsorbate-metal interfaces, relevant for a variety of research areas, from spintronics to catalysis, need to be reconsidered with many-particle effects being of utmost importance. These may affect chemisorption energy, spin transport, magnetic order, and even play a key role in the emergence of ferromagnetism at interfaces between non-magnetic systems.