Spin Thermoelectric Effects In Semiconductor Quantum Systerms

Spintronics is an expanding field in the solid-state physics aiming to develop novel devices,which utilize the charge and spin degrees of freedom of electrons. Due to the observation of spinSeebeck effect, spin thermoelectric effects become an active research area in recent years. In thefirst chapter, we briefly review the progress of spintronics and semiconductor quantum dot. Inthe second chapter, we introduce the thermoelectric effects.In chapter3, we study the thermal manipulation of pure spin current in a quantum dotattached to ferromagnetic leads. We found that quite large spin voltage can be generated with thehelp of temperature gradient and ferromagnetic electrodes. Furthermore, both the magnitude andthe signs of the spin voltage can be modulated by the temperature gradient. When the leads’magnetic moments are in antiparallel configuration, the spin voltage is greater than that obtainedin parallel configuration.In chapter4, we propose a pure thermoelectric spin generator based on a Rashba quantumdot molecular junction by using the temperature difference instead of the usual voltage bias. It isfound that a pure spin-up (spin-down) Seebeck coefficient can be generated by the coaction ofthe magnetic flux and the Rashba spin-orbit (RSO) interaction.In chapter5, we study the spin accumulation in a quantum dot (QD) by the temperaturedifference between the two ferromagnetic leads connected to the dot. We found two ways toreverse the spin accumulation: one is by adjusting the QD energy level with fixed temperaturegradient, and the other is by reversing the temperature gradient direction for fixed value of dotlevel. The spin accumulation in the QD can be enhanced by the magnitudes of both the leads’spin polarization and the asymmetry of the dot-lead coupling strengths.