Aligia, Armando

Date:    Thursday, August 18, 2022
Time:   14:00
Place:   ETH Zurich, Campus Hönggerberg, HPF G 6
Host:    Tilman Esslinger

New results on the Kondo effect in systems with atoms and molecules on
metallic surfaces and application to STM experiments

Armando Aligia
Centro Atómico Bariloche, INN, CNEA, CONICET, ARGENTINA

After a brief introduction to the Kondo effect, I will briefly explain the explanations so far proposed for the presence of a peak or a dip in the differential conductance dI/dV near V=0 observed by STM. Recently, 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].

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]. Other systems show similar behaviors.

[1] J. Fernández, P. Roura-Bas, and A. A. Aligia, Phys. Rev. Lett. 126, 046801 (2021).
[2] M. S. Tacca et al., Phys. Rev. B 103, 245419 (2021).
[3] G. G. Blesio, L. O. Manuel, P. Roura-Bas, and A. A. Aligia, Phys. Rev. B 98, 195435 (2018), Phys. Rev. B 100, 075434 (2019)
[4] R. Zitko, G. G. Blesio, L. O. Manuel, and A. A. Aligia, Nature Commun. 12, 6027 (2021)