Nanomechanical dissipation at a tip-induced Kondo onset

Abstract

The onset or demise of Kondo effect in a magnetic impurity on a metal surface can be triggered, as sometimes observed, by the simple mechanical nudging of a tip. Such a mechanically-driven quantum phase transition must reflect in a corresponding mechanical dissipation peak; yet, this kind of signature has not been focused upon so far. Aiming at the simplest theoretical modelling, we treat the impurity as an Anderson impurity model, the tip action as a hybridization switching, and solve the problem by numerical renormalization group. Studying this model as function of temperature and magnetic field we are able to isolate the Kondo contribution to dissipation. While that is, reasonably, of the order of the Kondo energy, its temperature evolution shows a surprisingly large tail even above the Kondo temperature. The detectability of Kondo mechanical dissipation in atomic force microscopy is also discussed. arXiv:1703.06057v2 [cond-mat.str-el]

Finite-frequency dissipation in a driven Kondo model

“…In this limit τ → ∞, we also have at our disposal the results of Ref. 1 , where we computed E diss for a SIAM with NRG, which gives numerically exact results. In that situation, the dissipation contained a large term proportional to Γ, plus a smaller Kondo contribution proportional to T K , albeit with logarithmic corrections not expressable as log T K , since the Kondo resonance is not simply a Lorentzian.…”

“…In our previous work 1 we treated the same problem in the limit of vanishing frequencies, which is relevant when the Kondo effect can be switched on and off mechanically, as in an AFM experiment. Under the hypothesis of thermalization, we found that the dissipated energy is:…”

“…We found in Ref. 1 that, when computing the energy dissipation in the static limit from Eq. ( 7) for a SIAM using NRG, the results could be easily interpreted in terms of the sum of contributions from the Hubbard bands, with energy ± d and hybridization Γ, and from the Kondo peak, with zero energy and hybridization T K , where T K Γ is the Kondo energy scale.…”

“…Following the first part of the paper, and Ref. 1 , we are going to study a hybridization quench, in which we suddenly change the hybridization from V 0 (leading to…”

“…In a previous paper 1 we used a simple approach to compute the mechanical energy dissipation associated with processes where one could switch on and off the Kondo effect experienced by electrons in, e.g., a tip-operated metal-metal contacts through magnetic impurities. That kind of mechanica manipulation can of course assumed to involve timescales much larger than the typical electronic ones, whereby we could show that an equilibrium calculation is enough to get to the Kondo dissiption result.…”