Condensed Matter Physics Seminar

The potential of metallic nanostructures to act as effective optical and infrared (IR) field transmitters, receivers, or enhancers has stimulated considerable research effort. Collective oscillations of valence electrons in metallic materials, also known as plasmons, determine the optical response of these materials. The energy and strength of these surface oscillations are a function of the shape, size and coupling of the nanoparticles. We calculate light scattering and surface modes in nanostructures that are commonly used as hosts and/or samples in different field-enhanced scanning probe microscopies and spectroscopies of molecular groups. The light scattering and near field distribution of particles such as nanorings [1], nanorods [2], nanodisks, or nanowires [3] are calculated and interpreted in terms of the plasmon modes supported by the nanosystems. The results are related for each case with different spectroscopic experiments and connected with the capabilities of these structures to host biomolecules and perform the corresponding spectroscopy, such as in Surface-enhanced Raman scattering (SERS). We obtain different optical and infrared contrast for different particle size and substrate material, and associate these differences in contrast to the properties of the tip-particle-substrate coupling [4]. Last, but not least, we address the spectral features of nanowire-like antenna resonances [5]. We focus on the departure of the plasmon resonances from standard l/2 antenna theory, both in the optical and infrared regimen. Depending on rod thickness, the antenna resonance follows different linear behavior, from L