Optical manipulation of parallel thermoelectric effect in a nanoscale three-terminal junction

• The new parallel thermoelectric structure is put forward.
• The polarized light and the increase of magnetic polarization cause the better thermoelectric performance.
• The polarized light can be favor of obtaining the lager spin thermoelectric efficiency.
• The system may be used as a high-efficiency spin thermoelectric device.

We propose a hybrid thermoelectric system based on extending two-terminal thermoelectric structure to three-terminal one where a quantum dot is coupled to a normal-metal lead and two ferromagnetic electrodes with noncollinear magnetic moments, the thermoelectric properties of this parallel thermoelectric system which is subject to a continuous polarized light are theoretically investigated. Within the nonequilibrium Green’s function theory, analytical expressions for thermoelectric coefficients are derived at length, which provides a powerful tool for further numerical calculations of thermoelectric properties. Some interesting thermoelectric features are reported and elucidated. We find that the polarized light can induce the Fano-like resonance in the spectrum of the electrical conductance and the thermal conductance, the thermopower and the charge figure of merit may be enhanced near the Fano-like resonance. Our results show that the polarized light and the increase of magnetic polarization are favor of achieving the better thermoelectric performance which indicates the strong violation of the Wiedemann–Franz law, especially, a significant enhancement of the spin thermal efficiency (spin figure of merit) can be obtained. We also analyze the dependence of thermoelectric features on the noncollinearity, it is found that the configuration of two ferromagnetic leads and the polarized light can jointly determine the thermoelectric features of this system, and the parallel configuration is best for obtaining the enhancement of spin figure of merit. Moreover, the polarized light can be favor of obtaining the lager spin thermoelectric efficiency at relatively high temperature. Therefore, the parallel thermoelectric structure may be used as a high-efficiency spin thermoelectric conversion device under certain circumstances.