Ultrafast Phase Transition via Catastrophic Phonon Collapse Driven by Plasmonic Hot-Electron Injection
Ultrafast Phase Transition via Catastrophic Phonon Collapse Driven by Plasmonic Hot-Electron Injection
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DOI：
10.1021/nl4044828
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发表时间：
2014-03-01
期刊：
影响因子：
10.8
通讯作者：
Haglund, Richard F., Jr.
中科院分区：
文献类型：
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作者：
Appavoo, Kannatassen;Wang, Bin;Haglund, Richard F., Jr.
超快光致相变可以通过以太赫兹速度调制集成纳米电路中的信号来彻底改变数据存储和电信技术。在量子相变材料（PCM）中，微观电荷、晶格和轨道自由度协同作用以改变宏观电学和光学性质。虽然这些相互作用是有据可查的散装单晶和薄膜，很少有人知道的超快动力学的纳米结构相变材料时，接口到另一类材料，在这种情况下，以积极的等离子体激元元素。在这里，我们演示了如何网格的金纳米粒子，作为一个等离子体光电阴极，诱导超快相变纳米结构的二氧化钒（VO 2）的光谱共振飞秒激光脉冲照射时。由金纳米网中的表面等离子体共振的光激发产生的热电子被弹道地注入穿过Au/VO 2界面以诱导VO 2中的亚皮秒相变。密度泛函计算表明，注入电子的临界密度导致6 THz声子模的灾难性崩溃。这在不同的实验中与VO 2相变有关。由光诱导电子注入引发的亚皮秒相变的演示打开了设计具有独特非平衡特性的混合纳米结构的可能性，作为具有可优化开关阈值的全光学纳米光子器件的关键步骤。
Ultrafast photoinduced phase transitions could revolutionize data-storage and telecommunications technologies by modulating signals in integrated nanocircuits at terahertz speeds. In quantum phase-changing materials (PCMs), microscopic charge, lattice, and orbital degrees of freedom interact cooperatively to modify macroscopic electrical and optical properties. Although these interactions are well documented for bulk single crystals and thin films, little is known about the ultrafast dynamics of nanostructured PCMs when interfaced to another class of materials as in this case to active plasmonic elements. Here, we demonstrate how a mesh of gold nanoparticles, acting as a plasmonic photocathode, induces an ultrafast phase transition in nanostructured vanadium dioxide (VO2) when illuminated by a spectrally resonant femtosecond laser pulse. Hot electrons created by optical excitation of the surface-plasmon resonance in the gold nanomesh are injected ballistically across the Au/VO2 interface to induce a subpicosecond phase transformation in VO2. Density functional calculations show that a critical density of injected electrons leads to a catastrophic collapse of the 6 THz phonon mode., which has been linked in different experiments to VO2 phase transition. The demonstration of subpicosecond phase transformations that are triggered by optically induced electron injection opens the possibility of designing hybrid nanostructures with unique nonequilibrium properties as a critical step for all-optical nanophotonic devices with optimizable switching thresholds.