arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2003.03611cond-mat.mes-hall
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半导体量子点-金属纳米壳复合物中等离子体辅助的双光子吸收

Plasmon-assisted two-photon absorption in a semiconductor quantum dot -- metallic nanoshell composite

Bintoro S. Nugroho, Alexander A. Iskandar, Victor A. Malyshev, Jasper Knoester

摘要:

光子吸收具有许多实际应用的潜力。我们从理论上研究了半导体量子点-金属纳米壳复合材料在共振连续波激发下这种现象的发生。该系统中的双光子吸收可以以两种方式发生:非相干-由于连续的基态到一个激子到双激子跃迁,以及相干-由于相干双光子过程,涉及量子点中的直接基态到双激子跃迁。在量子点附近的纳米壳层的存在引起两个主要效应:(i)-所施加的场振幅的重正化和(ii)-量子点的共振频率和辐射弛豫速率的重正化,两者都取决于量子点能级的布居。我们表明,在微扰制度,当激子能级只有轻微的人口,这些因素中的每一个可能会引起抑制或增强的双光子吸收。两者的复杂相互作用决定了最终的效果。超出微扰制度,它被发现,双光子吸收经历了剧烈的增强,这发生独立的类型的激发,无论是到单激子共振或到双光子共振。从两种纳米颗粒之间的耦合中出现的复合材料的双光子吸收的其他特征是双稳态和自振荡。

英文摘要:

Tho-photon absorption holds potential for many practical applications. We theoretically investigate the onset of this phenomenon in a semiconductor quantum dot -- metallic nanoshell composite subjected to a resonant CW excitation. Two-photon absorption in this system may occur in two ways: incoherent -- due to a consecutive ground-to-one-exciton-to-biexciton transition and coherent -- due to a coherent two-photon process, involving the direct ground-to-biexciton transition in the quantum dot. The presence of the nanoshell nearby the quantum dot gives rise to two principal effects: (i) -- renormalization of the applied field amplitude and (ii) -- renormalization of the resonance frequencies and radiation relaxation rates of the quantum dot, both depending on the the quantum dot level populations. We show that in the perturbation regime, when the excitonic levels are only slightly populated, each of these factors may give rise to either suppression or enhancement of the two-photon absorption. The complicated interplay of the two determines the final effect. Beyond the perturbation regime, it is found that the two-photon absorption experiences a drastic enhancement, which occurs independently of the type of excitation, either into the one-exciton resonance or into the two-photon resonance. Other characteristic features of the two-photon absorption of the composite, emerging from the coupling between both nanoparticles, are bistability and self-oscillations.

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