Regensburg 2019 – scientific programme

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MA: Fachverband Magnetismus

MA 45: Focus Session: Spins on Surfaces I (joint session O/MA)

MA 45.9: Talk

Thursday, April 4, 2019, 12:45–13:00, H15

Renormalization of single-ion magnetic anisotropy by charge fluctuations — •David Jacob — Dpto. de Física de Materiales, Universidad del País Vasco UPV/EHU, San Sebastián, Spain — IKERBASQUE, Basque Foundation for Science, Bilbao, Spain

Inelastic spin-flip excitations associated with single-ion magnetic anisotropy of quantum spins can be strongly renormalized by Kondo exchange coupling to the conduction electrons in the substrate, as shown recently for the case of Co adatoms on CuN₂ islands [1]. In this case, differential conductance spectra show zero-bias anomalies due to a Kondo effect of the doubly degenerate ground state, and finite-bias step features due to spin-flip excitations. Here I consider spin-1 quantum magnets with positive uniaxial anisotropy, where the ground state is nondegenerate and hence the Kondo effect does not take place [2]. Nevertheless, despite the absence of Kondo effect the magnetic anisotropy can still be strongly renormalized, both by exchange coupling to the conduction electrons and also by charge fluctuations. Interestingly, in contrast to the renormalization by Kondo exchange, charge fluctuations lead to asymmetric spectra, which, for strong charge fluctuations, mimic Fano-Kondo lineshapes, even though the origin is completely different.

References: [1] J. C. Oberg et al., Nature Nanotechnol. 9, 64 (2014); [2] D. Jacob, Phys. Rev. B 97, 075428 (2018)