Metallic nanoantennas have been studied as efficient coherent phonon generators and detectors, harnessing their characteristic optical absorption and polarization dependence of the optical modes. The ability to control the excitation of phononic modes depends on the properties of the multiple optical resonances of the system. Lately, it has been made possible to optimally excite and detect phonon modes via plasmon resonances at the same optical frequency using chiral nanostructures and circularly polarized light. However, torsional modes remain elusive in nanophononic studies. In this work we present a simple system composed of two coupled bars, where torsional mechanical modes can be excited using light with null angular momentum. The twisting of the phononic mode is provided by the peculiar symmetry of the mechanical eigenmode due to the interaction of the bars via either the substrate or a central connector.
We will present a complete theoretical analysis of the phononic and plasmonic modes, their surface deformation field and electromagnetic field profiles.
|