單量子點之光輔助穿遂現象的記憶效應：以廣義Floquet理論分析

Abstract

本文利用廣義Floquet理論研究單一量子點的傳輸行為，尤其著重於光子輔助穿遂現象的記憶效應。藉由廣義Floquet理論，我們可以將一具週期性的薛丁格方程，改寫成一個與時間無關且無限維度的等效方程。利用微擾分析得到解析結果，進而推導出包含記憶效應之電流與穿遂係數表示式。在此架構下，我們探討記憶效應對光子輔助穿遂現象的影響，其中包含多光子同調穿隧截止現象、電流梯級現象、庫倫阻塞現象。另外，我們探討溫度對於電子傳輸的影響。

The generalized Floquet approach is extended to sutdy the memory effect beyond the wide band limit on the photon-assisted electron tunneling through a periodically driven single quantum dot. An analytical Tien-Gordon-like expression, including the memory effect, for the current and transmission coefficient is derived based on the generalized Van Vleck (GVV) nearly degenerate perturbation theory. As a result, multiphoton (MP) coherent destruction of tunneling (CDT) phenomenon for small bias voltage is predicted by the transmission coefficients for the respective scattering channels. Numerically converged simulations and GVV analytical results are compared and both reveal that the memory effect leads to the suppression of the d.c. current stair-step jumps when varying the bias voltage on the single quantum dot. Furthermore, a novel blockade phenomenon that does not exist in the wide band limit is observed when the memory effect becomes significant, showing that the pumped current oscillate distinctively with respect to the gate voltage in the in the large bias limit. Finally, analytical expressions are obtained in the wide band limit, showing the temperature dependence of the conductance and current.