Two-channel Kondo tunneling in triple quantum dot

TL;DR

This paper investigates two-channel Kondo effects in a triple quantum dot system with odd electron occupation, analyzing its conductance behavior and mapping it onto an anisotropic two-channel Kondo model.

Contribution

It provides a detailed renormalization group analysis of the effective spin Hamiltonian and demonstrates the persistence of two-channel Kondo physics at low temperatures.

Findings

Two-channel Kondo physics persists at low temperatures.

System maps onto an anisotropic two-channel Kondo problem.

Conductance structure reveals Kondo behavior at various regimes.

Abstract

The effective spin Hamiltonian of a triple quantum dot with odd electron occupation weakly connected in series with left ($l$) and right ($r$) metal leads is composed of two-channel exchange and co-tunneling terms. Renormalization group equations for the corresponding three exchange constants $J_{l}$, $J_{r}$ and $J_{lr}$ are solved (to third order). Since $J_{lr}$ is relevant, the system is mapped on an anisotropic two-channel Kondo problem. The structure of the conductance as function of temperature and gate voltage implies that in the weak and intermediate coupling regimes, two-channel Kondo physics persists at temperatures as low as several $T_{K}$. At even electron occupation, the number of channels equals twice the spin of the triple dot (hence it is a fully screened impurity).