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arXiv 1010.5871cond-mat.mes-hall
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单量子点光子辅助隧穿的记忆效应:推广的Floquet理论方法

Exploration of the memory effect on the photon-assisted tunneling via a single quantum dot: A generalized Floquet theoretical approach

Hsing-Ta Chen, Tak-San Ho, Shih-I Chu

摘要:

采用推广的Floquet方法研究了电极-多级量子点-电极纳米量子器件中周期性驱动单个量子点的记忆效应对电子输运的影响.记忆效应的处理使用多功能洛伦兹谱密度(LSD)模型,该模型模拟的多个洛伦兹函数的每个电极的谱密度。对于对称单函数LSD模型,涉及一个单能级点,底层的单粒子传播子被证明是相关的2 × 2有效的时间依赖的哈密顿量,包括周期性的外部场和电极记忆效应。利用广义Van Vleck(GVV)近似简并微扰理论,导出了任意阶多光子共振直流隧穿电流的类Tien-Gordon解析表达式.数值收敛模拟和GVV分析结果符合得很好,揭示了多光子相干破坏隧穿的起源,并解释了记忆效应对直流电流阶梯跃变的抑制。特别地,观察到一种新的阻塞现象,在大的偏置电压限制下,场感应电流显示出独特的振荡。

英文摘要:

The generalized Floquet approach is developed to study memory effect on electron transport phenomena through a periodically driven single quantum dot in an electrode-multi-level dot-electrode nanoscale quantum device. The memory effect is treated using a multi-function Lorentzian spectral density (LSD) model that mimics the spectral density of each electrode in terms of multiple Lorentzian functions. For the symmetric single-function LSD model involving a single-level dot, the underlying single-particle propagator is shown to be related to a 2 x 2 effective time-dependent Hamiltonian that includes both the periodic external field and the electrode memory effect. By invoking the generalized Van Vleck (GVV) nearly degenerate perturbation theory, an analytical Tien-Gordon-like expression is derived for arbitrary order multi- photon resonance d.c. tunneling current. Numerically converged simulations and the GVV analytical results are in good agreement, revealing the origin of multi- photon coherent destruction of tunneling and accounting for the suppression of the staircase jumps of d.c. current due to the memory effect. Specially, a novel blockade phenomenon is observed, showing distinctive oscillations in the field-induced current in the large bias voltage limit.

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