Speaker
Description
Large electron densities are known to increase the significance of interactions, which often leads to instabilities in the simple Fermi liquid state. One way to achieve high electron densities is to tune the system to exhibit a Van Hove singularity (VHS) close to the Fermi level. VHSs are particularly pronounced in systems of reduced dimensionality. We propose an experimental setup consisting of an adatom positioned between two zigzag graphene nanoribbons (ZGNRs) [1] and coupled to the edge states in the topological Zak phase [2], where our numerical renormalization group theory predicts interesting interplay between Kondo effect and the multipied VHSs. We demonstrate that by using the known evolution of the ZGNR spectrum with transverse electric fields into a half-metallic state, one can tune the types and positions of VHSs in each spin channel. This provides an exotic electronic bath for a magnetic adatom. In particular, due to the power-law diverging density of states in the nanoribbon, the Kondo temperature is strongly enhanced, but the usual Kondo peak in local spectrum is replaced by a power-law pseudo-gap, which could be observed e.g. through scanning tunneling spectroscopy. We will present predictions for even more exotic situations that can be accessed by tuning electric fields. Our goal is to motivate experimental efforts in this direction.
[1] Y.-W. Son, M. L. Cohen and S. G. Louie, Nature 347, 444 (2006).
[2] P. Delplace, D. Ullmo, G. Montambaux, Phys. Rev. B 84, 195452 (2011).
Acknowledgements:
This work has been supported by National Science Centre in Poland through grant no. 2023/51/D/ST3/00532
