開放式量子環中的量子傳輸

Abstract

本論文研究電子在開放式量子環中的傳輸特性。對於開放式量子環在零磁場時，我們可以發現其共振態符合封閉環的束縛態。並且在兩邊通道(lead)不對稱以及環的通道大小改變時，可以發現Fano結構。然而我們可以藉由改變環的對稱來調整Fano結構使其由寬變尖，亦可以讓環的通道變寬而使得Fano結構由尖變寬。在趨進一維的情形，共振峰變的較尖銳且向左移而接近封閉環的束縛態。對於開放式量子環在有限磁場下，我們可以發現AB效應而且其振盪周期為 。然而值得注意的是在高磁場的情況下，並無周期振盪的情形。假如我們改變兩邊通道的相對角度，我們可以發現在高磁場的情況下對角度比較不敏銳，但在低磁場的時候則是相反。

We study quantum transport properties of an open quantum ring(OQR). For the OQR in zero magnetic filed, we have found that the resonant peaks correspond to the bond states of a close ring. Fano structure in the transmission of an OQR can be found in two case which the two lead are configured asymmetrically and the channel size of ring is changed. Moreover, we can tune the Fano structure from broad to sharp by varying the symmetry of OQR and tune the Fano structure from sharp to broad by widening the channel width of the ring. Then approaching to 1D case, the resonance peaks become shaper and shift toward the left to be close to bound of close ring, when the channel narrow down. For the OQR with finite magnetic filed, We have found that the AB effect when the external field are applied in the ring and the oscillating period . And it should be noted that the periodic oscillations are disappear at high magnetic field. If we change the angle of two lead for low and high magnetic field, we can found that it is sensitive to changing angle for small magnetic field but not for large magnetic field.