Colossal enhancement in thermoelectric effect in a laterally coupled double-quantum-dot chain by the Coulomb interactions

• Coulomb interactions split the double-peak structure of the Seebeck coefficient.
• Coulomb interactions resulting in a strongly violation of the Wiedemann–Franz law.
• Coulomb interactions lead to a colossal enhancement in the figure of merit.

Thermoelectric effects, including Seebeck coefficient (S), thermal conductance (κ), and figure of merit (ZT), in a laterally coupled double-quantum-dot (DQD) chain with two external nonmagnetic contacts are investigated theoretically by the nonequilibrium Green's function formalism. In this system, the DQD chain between two contacts forms a main channel for thermal electrons transporting, and each QD in the main chain couples laterally to a dangling one. The numerical calculations show that the Coulomb interactions not only lead to the splitting of the asymmetrical double-peak structure of the Seebeck coefficient, but also make the thermal spectrum show a strong violation of the Wiedemann–Franz law, leading to a colossal enhancement in ZT. These results indicate that the coupled DQD chain has potential applications in the thermoelectric devices with high thermal efficiency.