Filters

2022 - 20242

More filters

2022 - 20242
Reset filters

Settings

Author: Petersen, Thorben × DDC: 530 ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Coulomb exchange as source of Kitaev and off-diagonal symmetric anisotropic couplings
    (London : Springer Nature, 2024) Bhattacharyya, Pritam; Petersen, Thorben; Bogdanov, Nikolay A.; Hozoi, Liviu
    Exchange underpins the magnetic properties of quantum matter. In its most basic form, it occurs through the interplay of Pauli’s exclusion principle and Coulomb repulsion, being referred to as Coulomb or direct exchange. Pauli’s exclusion principle combined with inter-atomic electron hopping additionally leads to kinetic exchange and superexchange. Here we disentangle the different exchange channels in anisotropic Kitaev–Heisenberg context. By quantum chemical computations, we show that anisotropic Coulomb exchange, completely neglected so far in the field, may be as large as (or even larger than) other contributions — kinetic exchange and superexchange. This opens new perspectives onto anisotropic exchange mechanisms and sets the proper conceptual framework for further research on tuning Kitaev–Heisenberg magnetism.
  • Thumbnail Image
    Item
    Quantum chemical insights into hexaboride electronic structures: correlations within the boron p-orbital subsystem
    (London : Springer Nature, 2022) Petersen, Thorben; Rößler, Ulrich K.; Hozoi, Liviu
    The notion of strong electronic correlations arose in the context of d-metal oxides such as NiO but can be exemplified on systems as simple as the H2 molecule. Here we shed light on correlation effects on B62− clusters as found in MB6 hexaborides and show that the B 2p valence electrons are fairly correlated. B6-octahedron excitation energies computed for CaB6 and YbB6 agree with peak positions found by resonant inelastic x-ray scattering, providing a compelling picture for the latter. Our findings characterize these materials as very peculiar p-electron correlated systems and call for more involved many-body investigations within the whole hexaboride family, both alkaline- and rare-earth compounds, not only for N- but also (N ± 1)-states defining e. g. band gaps.