介觀系統中電偶極引起的自旋共振

Abstract

此論文主要探索在經過Rashba形式量子通道的介觀傳輸系統中由電偶極引起的自旋共振（EDSR）現象。EDSR的形態包含了沿著通道方向的一個靜態的磁場和一個平行於磁場的交流電場。 用時間微擾產生出的旁帶（sideband）研究了傳輸後波函數的自旋翻轉。在入射能量因微擾而落到黎曼間隙外（旁帶能量為ε±ω）的情況下，上旁帶和下旁帶包含了intraband（interbabd）躍遷此無（有）自旋翻轉。 我們主要的發現在自旋翻轉共振特徵存在，當能量吻合黎曼間隙的邊緣或是副帶（sideband）的底端，也就是狀態密度很大的時候。更進一步發現自旋密度在空間有震盪現象是基於由有自旋翻轉和無自旋翻轉的波函數的干涉產生出的。 此外，由上下（ε±ω）兩旁帶的自旋密度震盪產生的干涉會有自旋密度拍（beat）。 次之，我們的計算包括evanescent modes 的效應。我們做了仔細的evanescent modes分析，在能量低於副帶底的時候，縱方向波量kx被發現是複數而非存虛數。

This thesis seeks after the manifestation of the electric-dipole-induced spin resonance (EDSR) in mesoscopics transport through a Rashba-type quantum channel. The EDSR con‾guration involves a static ‾eld along the channel and an ac electric ‾eld in parallel with the magnetic ‾eld. Within a time dependent perturbation that induces first sideband, we study the spin fipping in the transmitted wavefunctions. For the case when the incident energy falls within the Zeeman gap, and the sideband energies （ε±ω） outside of it, both the upper and lower sideband involves intraband (interband) transition which is nonspin (spin) fipping. Our major fnding is that the spin fipping component exhibits resonance characteristics when the sideband energy coincides with either the Zeeman gap edges or the subband bottom, when the density of state is large. Furthermore, the spin density oscillates in space according to the interference between the spin fipping and non-spin fipping comments. Additional beating features in the spin density spatial pro‾le is found to result from the interference between the spin density oscillations due to （ε+ω）and （ε-ω） sidebands. Our calculation has incorporated the effects of evanescent modes. We have performed a detail analyze on the evanescent modes. The longitudinal wavevector kx is found to be complex rather then pure imaginary.