A5: Optical conductivities and entanglement in magnetic topological semimetals
Liviu Chioncel, Markus Heyl
In this project we study a variety of topological materials from the family of the Kagome magnets which are relevant for the experimental efforts of the overall project. In this context our aim is twofold. First, we plan to develop and apply material-specific theoretical tools with predictive power for spectral probes, i.e., diagonal and off-diagonal conductivities. This will be achieved by performing material-specific as well as model calculations combining Density Functional Theory with many body physics using Dynamical Mean Field Theory and its cluster extensions. Second, we aim to use these methods in order to make material-specific predictions on multipartite quantum entanglement through the quantum Fisher information.
Publications
2024 |
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Prodan, L.; Chmeruk, A.; Chioncel, L.; Tsurkan, V.; Kézsmárki, I. Anisotropic charge transport in the easy-plane kagome ferromagnet Fe3Sn Journal Article Phys. Rev. B 110, 094407, 2024. @article{prodan_anisotropic_2024, | |
Jones, D.; Östlin, A.; Weh, A.; Beiuşeanu, F.; Eckern, U.; Vitos, L.; Chioncel, L. Superconducting transition temperatures of pure vanadium and vanadium-titanium alloys in the presence of dynamical electronic correlations Journal Article Phys. Rev. B 109, 165107, 2024. @article{jones_superconducting_2024, Ordinary superconductors are widely assumed insensitive to small concentrations of random nonmagnetic impurities, whereas strong disorder suppresses superconductivity, ultimately leading to a superconductor-insulator transition. In between these limiting cases, a most fascinating regime may emerge where disorder enhances superconductivity. This effect is discussed here for the β phase of vanadium-titanium alloys. Disorder is modeled using the coherent potential approximation while local electronic interactions are treated using dynamical mean-field theory. The McMillan formula is employed to estimate the superconducting transition temperature, showing a maximum at a Ti concentration of around 0.33 for a local Coulomb interaction U in the range of 2 eV to 3 eV. Our calculations quantitatively agree with the experimentally observed concentration-dependent increase of Tc, and its maximal value of about 20%. | |
2023 |
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Prodan, L.; Evans, D. M.; Griffin, S. M.; Oestlin, A.; Altthaler, M.; Lysne, E.; Filippova, I. G.; Shova, S.; Chioncel, L.; Tsurkan, V.; Kézsmárki, I. Large ordered moment with strong easy-plane anisotropy and vortex-domain pattern in the kagome ferromagnet Fe3Sn Journal Article Appl. Phys. Lett. 123, 021901, 2023. @article{prodan_large_2023, We report the magnetic anisotropy of kagome bilayer ferromagnet Fe3Sn probed by the bulk magnetometry and magnetic force microscopy (MFM) on high-quality single crystals. The dependence of magnetization on the orientation of the external magnetic field reveals strong easyplane magnetocrystalline anisotropy and anisotropy of the saturation magnetization. The leading magnetocrystalline anisotropy constant shows a monotonous increase from K-1 approximate to -1.0 x 10(6) J/m(3) at 300K to -1.3 x 10(6) J/m(3) at 2K. Our ab initio electronic structure calculations yield the value of total magnetic moment of 7.1 mu(B)=f.u. and a magnetocrystalline anisotropy energy density of -0.57meV=f.u. (-1.62 x 10(6)J/m(3)) both being in reasonable agreement with the experimental values. The MFM imaging reveals micrometer-scale magnetic vortices with weakly pinned cores that vanish at the saturation field of similar to 3T applied perpendicular to the kagome plane. The observed vortex-domain structure is well reproduced by the micromagnetic simulations, using the experimentally determined value of the anisotropy and exchange stiffness. (c) 2023 Author(s). |