全電性自旋流量測的研究

Abstract

我們提出了一種全電性量測交流自旋流(alternating spin current)的方法並且理論計算出交流自旋流所產生的電信號。我們的系統主要利用半導體中的自旋軌道交互作用，以平面二維電子氣(two-dimension electron gas)夾在兩個金屬閘極中間作為測量裝置，在這樣結構中的電磁波為波導的模態。我們研究在自旋極化方向與流動方向相互垂直並且躺在二維電子氣平面中的自旋流，這樣的交流自旋流會激發出光子，只有對應於橫向磁場的波導模式(transverse magnetic modes)的光子才被激發。光子在兩個閘極之間產生交替的電位差，而此電位差是可以用實驗去量測的。

We propose a pure electrical means of detecting an alternating (ac) spin current, and we perform theoretical calculations on the order of magnitude of the expected electrical signal. Our proposed scheme has employed the spin-orbit interaction in semiconductors. The proposed measurement device consists of a two-dimensional electron gas (2DEG) sandwiched between two metallic gates such that the electromagnetic waves in between the gates are waveguide modes. An ac in-plane spin current, with both spin and flow direction orthogonal to each other and in the plane of the 2DEG, passes through the structure is found to excite photons. Only photons corresponding to the transverse magnetic (TM) waveguide modes are excited. These excitations give rise to an ac electrical potential difference between the two metal gates. The potential difference is found to be measurable by present day experimental capability.