閘極局域之介觀系統的自旋相關物理性質探討

Abstract

我們將針對一系列以閘極局域的量子線與其他介觀系統做系統性的研究其自旋相關的物理參數，一般即使在沒有鐵磁性接點和外加磁場下，自我存在的自旋束縛態或自旋軌道耦合都有可能產生自旋極化電流；我們將釐清二維電子氣與類一微量子線各自之自旋相關的物理參數如何隨電子濃度而改變，另外藉由在一維量子線上外加不均勻且垂直通道的電場將可增強Rashba 自旋軌道作用，以此控制自旋軌道耦合強度並系統性探討其對0.7電導異常與零偏壓電導異常的影響，在微結構中的局域電子自旋極化來自多體之間的交互作用，當電子密度減少，多體之間的交互作用就越強，之前實驗結果歸納得知電子的倍像散射會受微結構的幾何形狀影響，像量子線的長度就會增加其內部電子的背向散射，因此量子線的自旋極化值會因電子密度、幾何長度與其閘及電壓在空間的相對分佈而有所不同。我們將系統性將樣品依展現的自旋相關物性歸類，並藉此也一併釐清0.7結構與一維量子線的基態；最後我們利用磁場聚焦技術來測量樣品的自旋極化值，希望藉由此研究工作，學會以電性測量有效地製造、操控、與偵測自旋極化電流。

In all, we propose to investigate spin-related physical quantities systematically in gate-confined quantum wires and other mesoscopic systems. Either intrinsic spin bound state or spin-orbit coupling may generate spin polarization current in nanostructures without ferromagnetic contacts and applied magnetic fields. The dependence of spin orbit interaction parameters on carrier density in a two dimensional electron gas and a quasi-one dimensional wire will be explored independently. The influence of Rashba spin-orbit interaction on 0.7 anomaly and zero bias anomaly will be studied by imposing the quantum wire with a nonuniform transverse electric field. Spin polarization of carriers in nanostructures can result from strongly enhanced many-body interactions, which arise when the carriers are confined in a quantum wire or a quantum dot. Many body interactions are predominantly influenced by carrier density in quantum wires. Our earlier work showed that electron backscattering depends on the wire geometry. Meanwhile, quantum wires of different carrier density and geometry with different arrangements of gate voltage will have different values of spin polarization. The degree of spin polarization among samples will be cataloged. Through this, we would figure out the origin of 0.7 structures and ground state of a one dimensional interacting wire. Finally, a magnetic focusing technique will be used to measure spin polarization. Through this work, we will learn how to effectively create, manipulate, and detect spin polarized currents by electrical means.