New results on the Kondo effect in systems with atoms and molecules on metallic surfaces

New results on the Kondo effect in systems with atoms and molecules on
metallic surfaces

Aligia A. A.
Centro Atómico Bariloche, CNEA, CONICET, ARGENTINA

I revise the arguments used to explain the presence of a peak or a dip in the differential conductance dI/dV near V=0 observed by STM.
Interpreting experiments for Co on Cu(111), in which an antiresonance in dI/dV at V=0 AND a resonance near the bottom of the conduction band are observed, we conclude by NRG calculations that the STM tip “sees” mainly the Co s electrons and the dip is due to interference effects [1]. This is confirmed by recent ab initio calculations [2].
In addition, from other NRG calculations in a spin-1 two-channel Kondo model with anisotropy D(SZ)2 we find a topological quantum phase transition in which the Kondo peak is suddenly turned to a dip with increasing D [3]. For large D the system is in a “non-Landau” Fermi liquid phase not adiabatically connected to a non-interacting system.
Extending the theory to non-equivalent orbitals and non-zero magnetic field we can explain several relevant experiments in Fe phthalocyanine [4].

[1] J. Fernández, P. Roura-Bas, and A. A. Aligia, Phys. Rev. Lett. 126, 046801 (2021).
[2] M. S. Tacca, T. Jacob, and E. C. Goldberg, Phys. Rev. B 103, 245419 (2021).
[3] G. G. Blesio et al., Phys. Rev. B 98, 195435 (2018); ibid 100, 075434 (2019).
[4] R. Zitko, G. G. Blesio, L. O. Manuel, and A. A. Aligia, ArXiv:2105.13248, submitted to Nature Commun.
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