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Author: Craco, Luis ×

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    All-t2g electronic orbital reconstruction of monoclinic MoO2 battery material
    (Basel : MDPI, 2020) Craco, Luis; Leoni, Stefano
    Motivated by experiments, we undertake an investigation of electronic structure reconstruction and its link to electrodynamic responses of monoclinic MoO2. Using a combination of LDA band structure with DMFT for the subspace defined by the physically most relevant Mo 4d-bands, we unearth the importance of multi-orbital electron interactions to MoO2 parent compound. Supported by a microscopic description of quantum capacity we identify the implications of many-particle orbital reconstruction to understanding and evaluating voltage-capacity profiles intrinsic to MoO2 battery material. Therein, we underline the importance of the dielectric function and optical conductivity in the characterisation of existing and candidate battery materials.
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    Nematic fluctuations in iron-oxychalcogenide Mott insulators
    (London : Nature Publishing Group, 2021) Freelon, B.; Sarkar, R.; Kamusella, S.; Brückner, F.; Grinenko, V.; Acharya, Swagata; Laad, Mukul; Craco, Luis; Yamani, Zahra; Flacau, Roxana; Swainson, Ian; Frandsen, Benjamin; Birgeneau, Robert; Liu, Yuhao; Karki, Bhupendra; Alfailakawi, Alaa; Neuefeind, Joerg C.; Everett, Michelle; Wang, Hangdong; Xu, Binjie; Fang, Minghu; Klauss, H.-H.
    Nematic fluctuations occur in a wide range physical systems from biological molecules to cuprates and iron pnictide high-Tc superconductors. It is unclear whether nematicity in pnictides arises from electronic spin or orbital degrees of freedom. We studied the iron-based Mott insulators La2O2Fe2OM2M = (S, Se), which are structurally similar to pnictides. Nuclear magnetic resonance revealed a critical slowing down of nematic fluctuations and complementary Mössbauerr spectroscopy data showed a change of electrical field gradient. The neutron pair distribution function technique detected local C2 fluctuations while neutron diffraction indicates that global C4 symmetry is preserved. A geometrically frustrated Heisenberg model with biquadratic and single-ion anisotropic terms provides the interpretation of the low temperature magnetic fluctuations. The nematicity is not due to spontaneous orbital order, instead it is linked to geometrically frustrated magnetism based on orbital selectivity. This study highlights the interplay between orbital order and spin fluctuations in nematicity.