Renormalization of single-ion magnetic anisotropy in the absence of Kondo effect

Physical Review B 97, 075428 (2018)

Renormalization of single-ion magnetic anisotropy in the absence of Kondo effect

D. Jacob

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. 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 non-degenerate and hence the Kondo effect does not take place. Nevertheless the renormalization of inelastic spin excitations due to Kondo exchange coupling still takes place despite the complete absence of the Kondo effect in the ground state. Additionally, I show that away from particle-hole symmetry, charge fluctuations have a similar effect as Kondo exchange coupling, leading to the renormalization of spin flip excitations. However, in contrast to the renormalization by Kondo exchange, charge fluctuations lead to asymmetric spectra, which for strong charge fluctuations can mimic Fano behavior.

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Doi
http://dx.doi.org/10.1103/PhysRevB.97.075428
arxiv
http://arxiv.org/abs/1712.01005

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