Thermoelectric Signatures of Kondo Physics in Geometry-Tunable Double Quantum Dots

TL;DR

The paper addresses how geometry-controlled coupling in a double quantum dot system affects Kondo physics and thermoelectric transport. It employs the non-crossing approximation in the $U\to\infty$ limit to analyze spectral density, $T_K$, occupations, Seebeck coefficient, and thermal conductance as the geometry parameter $p$ tunes from series to parallel. Key findings include the robustness of the central Kondo resonance, geometry- and inter-dot-tunable satellite peaks, sign reversals in the Seebeck coefficient, and a nonmonotonic thermal conductance with a maximum near $T\sim\Gamma$; these results highlight interference and coupling asymmetry as levers for nanoscale device optimization. The work provides a framework for geometry-based control of thermoelectric response and suggests directions for non-equilibrium studies and NRG benchmarking for quantitative validation.

Abstract

The equilibrium thermoelectric and spectral properties of a double quantum dot system are investigated, with the geometry continuously tuned from series to parallel via a parameter $ p $. Within the non-crossing approximation in the infinite-$ U $ limit, the Kondo peak remains robust, while satellite features and the Kondo temperature show strong sensitivity to the geometry. The Seebeck coefficient exhibits sign reversals and non-monotonic behavior as a result of the interplay between Kondo and satellite peaks. These findings underscore the role of interference and coupling asymmetry in governing transport properties, suggesting routes for geometry-based optimization in nanoscale devices.

Figures (10)

• Figure 1: (Color online) Schematic representation of the double quantum dot system connected in parallel to two metallic leads.
• Figure 2: (Color online) Spectral density for several values of $p$ in the case $t=0$. The panels separate the Kondo resonance around $\omega\approx 0$ (left) and the satellite peaks structures (right).
• Figure 3: (Color online) Spectral density for several values of $p$ with finite inter-dot coupling $t=1$. The panels separate the Kondo resonance around $\omega\approx 0$ (left) and the satellite peaks structures (right).
• Figure 4: (Color online) Kondo temperature vs $t$ for several values of $p$.
• Figure 5: Occupation number ($n_+$ and $n_-$) as a function of $t$ for various values of $p$ and $T/T_K=0.1$.