Ultrafast Phase Transition via Catastrophic Phonon Collapse Driven by Plasmonic Hot-Electron Injection

Abstract

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.

Harvesting the loss: surface plasmon-based hot electron photodetection

“…In plasmonic metamaterials, the nonradiative decay process will lead to optical absorption in the metal and reduced performance. Although much effort has been devoted to mitigating plasmon nonradiative decay, recent research has uncovered exciting opportunities for harnessing the process [27,34], such as in photothermal heat generation [35,36], photovoltaic devices [27,37], photocatalysis [38][39][40], driving material phase transitions [41,42], photon energy conversion [43], and photodetection [44][45][46][47][48][49][50]. For instance, the decay of hot electrons can lead to the local heating of the plasmonic nanostructures, making them candidates for nanoscale heat sources [35,36] for use in cancer therapy [51] and solar steam generation [52,53].…”

Sol-Gel Glasses Doped with Pt-Acetylides and Gold Nanoparticles for Enhanced Optical Power Limiting

“…Hot electrons A potential solution to the long range problem (question 5) would be excited electrons from the gold 1 [73]. This mechanism would be problematic to combine with question 4 and 1.…”

Ultrafast diffraction conoscopy of the structural phase transition in VO2 : Evidence of two lattice distortions

“…Out of these external excitations, light with ultra-short laser pulses allows monitoring the phase transition dynamics on ultrafast time scale [11]. In the past recent decades, several enthralling results on VO 2 , using optical [11][12][13][14][15][16][17], terahertz [18][19][20][21], Xray [10,[22][23][24][25][26][27], and electron diffraction [28][29][30] methods increased our understanding regarding its phase transition.…”