双量子点系统中热压作用下的自旋过滤效应

Spin-filtering effect in a double-quantum-dot structure subjected to thermal bias

研究与两个金属电极耦合的顺序连接双量子点系统中热压作用下的自旋极化电流.在震荡磁场的作用下,两个量子点之间的耦合强度变得和自旋有关,并对电流的强度和共振峰产生影响.在量子点内库伦相互作用为零时,随着两个量子点中不同自旋方向电子耦合强度差值的增大,自旋朝上的电流出现明显的双峰结构,而自旋朝下电流保持单峰结构,并且强度变弱,使得电流的自旋极化率增大,产生理想的自旋过滤效果.这种现象在器件两端的温度差较小的条件下也能够出现,是设计灵敏、低能耗的热自旋电子学器件的理想情况.量子点内的库伦相互作用会使得电流的峰产生进一步的分裂,从而在更多的量子点能级处出现一种自旋方向的电流为峰值,而一种自旋方向的电流为极小值的情况.通过调整量子点间自旋相关的耦合强度的符号,可以控制能够隧穿通过结构的电子的自旋方向.

Spin-polarized current in a serially connected double quantum dot coupled to two metal leads is studied.Under an oscillating magnetic field,the coupling strength between the two dots becomes spin-dependent,which can affect not only the magnitude but also the peaks′positions of the current.In the absence of the intradot Coulomb interaction,with increasing spin asymmetry of the interdot coupling strength,the spin-up current develops double-peak structure,whereas the spin-down one remains single-peak configuration with reduced current strength.As a result of it,the spin polarization of the current becomes larger,an idea condition for filtering electron spin.Such a phenomenon will emerge under small temperature difference between the two leads,and can be used for designing sensitive and lower energy consumption thermspin devices.The Coulomb interaction in the dots will further split the currents′peaks and enables the emerge of peak in one spin component current whereas that of the other spin direction remains a minimum value.By adjusting the sign of the spin-dependent interdot coupling strength,the spin direction of the transported current can be adjusted accordingly.