Modeling the effects of molecule distortion on the Kondo resonance in the conductance of CoPc/Au(111) and TBrPP‐Co/Cu(111)

Abstract

Recent scanning tunneling microscope (STM) experimental studies on transport through CoPc and TBrPP‐Co molecules adsorbed on metallic surfaces have reported several interesting results: (i) a high Kondo temperature as compared to those of adsorbed undressed magnetic atoms, (ii) the Kondo resonance shows up either as a Kondo peak (CoPc) or as a Fano dip (TBrPP‐Co), (iii) the Kondo temperature depends strongly on the molecule conformation and can be manipulated experimentally. Aiming to propose a theoretical framework that may serve to analyze these observations, we first discuss the case of an isolated magnetic atom adsorbed on a metallic surface. Much of the work on this simple case turns out to be of great help in the analysis of the more complex systems. Then, a simple model is proposed that, capturing the main features of the inner structure of the molecule (four lobe orbitals plus a strongly correlated orbital), offers a physical interpretation for most of the observations on those two moecules. In addition, it allows predicting the behavior of the system upon other symmetry or conformational changes, or when the STM tip is moved away from the Co atom.

Switching Molecular Kondo Effect via Supramolecular Interaction

“…The most-widely used method to compute Kondo temperature is a combination of DFT and numerical renormalization group (NRG) solution of the Anderson impurity model. − An alternative is to use Haldane expression, ,where Γ is the broadness of the impurity state, E d is the energy level of the impurity state with respect to the Fermi level ( E d < 0), and U is the on-site Coulomb repulsion energy. , According to eq , T K monotonically depends on Γ, and a smaller Γ leads to a lower Kondo temperature. T K dependence on U is not monotonic: exponential decays when U is small ( U < 2| E d |) and near linearly increases when U is large ( U > 2 | E d |).…”

Variation of Kondo Peak Observed in the Assembly of Heteroleptic 2,3-Naphthalocyaninato Phthalocyaninato Tb(III) Double-Decker Complex on Au(111)

“…However, Hualde et al demonstrated that the ligand–ligand interaction can explain the dip formation. − To examine whether their analysis can be applied to our system, we first investigate the ligand–ligand interaction in the 1D chain observed in our experiment.…”

“…Since the relative contribution of tip/Co/lobe/metal substrate path is stronger in the case of TBrPP-Co than that of CoPc, the Fano dip appears. They concluded that the role of the molecular lobes is not only to participate in the screening of the spin at the Co atom, as the metallic surface does, but also contributing to change dips into peaks or even to drive the system in/out of the Kondo regime. − …”