Topological-Mass Control of an Emergent Kondo Scale in an Interacting SSH Chain

Abstract

Topological bound states emerging at domain walls of dimerized chains provide a robust platform for exploring correlation effects beyond single-particle physics. When such a soliton state is coupled to a metallic substrate, local Coulomb interactions can give rise to Kondo screening. Here we demonstrate analytically and numerically that, in an interacting Su-Schrieffer-Heeger (SSH) chain, the Kondo temperature is directly controlled by the topological mass that governs the bulk gap. Near the topological transition, the Kondo scale collapses linearly with the mass parameter while retaining its exponential sensitivity to hybridization. This establishes a minimal mechanism by which a bulk topological parameter quantitatively determines an emergent many-body energy scale. Our results clarify the strong configuration dependence of soliton-induced Kondo signatures observed in graphene nanoribbon systems on Au(111) and provide experimentally testable predictions for scanning tunneling spectroscopy.

Figures (6)

• Figure 1: Chemical structures of the system in this work. (a) Molecular structure of Class-II OInIn isomers with alternating hopping amplitudes. (b) Schematic of a long chain formed by connecting these units. (c) Formation of a domain wall at the boundary between two distinct dimerization patterns. (d) Calculated energy spectrum of the SSH model ($t_1=2$, $t_2=1$) with 2N=128 sites, showing a clear midgap state at E=0 due to the topological defect. (e) Spatial distribution of the probability density $|\psi_i|^2$ for the soliton state (solid line) localized at the domain wall and the edge state (dashed line). Dotted lines represent the approximated solutions derived in the later section. (f) Conceptual illustration of the soliton orbital hybridized with the Au(111) substrate (modeled as a conduction bath), forming the basis for the effective Anderson impurity model.
• Figure 2: Kondo temperature $T_{\rm K}$ as a function of hybridization strength $\Gamma$ for representative effective Coulomb repulsions $U_{\rm eff}=0.2$, $0.3$, and $0.5$ eV, evaluated using Eq. (\ref{['eq:TK_PH']}). The strong exponential dependence implies that small variations in adsorption geometry can induce drastic changes in $T_{\rm K}$.
• Figure 3: Kondo temperature $T_{\rm K}$ as a function of topological parameter $r=t_1/t_2$ for $U=0.6$ eV, $\Gamma_0=0.005$ eV evaluated using Eq. \ref{['eq:TK_topo']}. The inset shows the enlarged view in the vicinity of the topological transition point $r=1$.
• Figure 4: Adsorption-height dependence of the Kondo temperature $T_{\rm K}$ on Au(111), assuming an exponential decay of the hybridization $\Gamma(z)\sim \Gamma_0 e^{-2\kappa z}$. A sub-Angström variation in adsorption height can suppress $T_{\rm K}$ by several orders of magnitude.
• Figure 5: Representative Fano lineshapes for different values of the asymmetry parameter $q$ with $a=1$, $b=0$, $V_0=0$, and $\Gamma_{\rm K}=5$ meV. The Kondo resonance can appear as either a peak or a dip depending on tunneling interference.