Real-time tuneable bright bonding plasmonic modes in Ga nanostructures

Abstract: The precise control of nanogaps is crucial for plasmonic nanoassemblies, where plasmon hybridization is highly sensitive to gap size and geometry. This sensitivity enables fine-tuning of the resonance wavelength and near-field enhancement, offering the potential for advanced optical applications. However, conventional lithographic techniques for gap modulation are constrained to discrete values and face challenges in achieving nanometer order of separations. Such limitations hinder the comprehensive study of plasmon coupling across varying interaction regimes. Overcoming these challenges is essential for advancing nanoplasmonic research and its practical applications. Herein, we demonstrate a tuneable plasmonic device in which real-time tunability of this hybridization mode is achieved via manipulation of the inter-droplet gap of liquid metal nanoparticles by macroscopic physical deformation. In particular, we show that the optical spectra obtained from the sample shift towards higher energy on the application of a linear strain, resulting in an increase of inter-droplet gaps leading to a direct probing of the bright modes in situ. Our method thus offers a novel means of exploring the fundamental concept of real-time tuneable plasmon hybridization as well as tuning of nanoparticle assembly with any desired gap in a controlled manner.