New technique for studying phonon modes in nanomaterials is demonstrated

Vibrations in a nanomaterial can modify its electronic properties as well as electronic interactions with neighboring materials. Understanding these vibrations is challenging because they are extremely fast, with periods in the picosecond scale.

By developing a new technique known as oscillation associated spectrum (OAS) analysis, researchers Kirschner et al. look to better understand the phase and relative magnitude of changes induced by these vibrations and reveal information about the optoelectronic and mechanical properties of nanoparticles. The new method is purposefully simplistic and does not make assumptions such as prescribing line shapes for the observed spectral features associated with coherent-phonon oscillations, making the method highly adaptive.

To test this technique, the authors applied their approach to acoustic phonons that modulate plasmon-exciton coupling. They analyzed the optical signatures of coherent acoustic phonons in nanoparticles using OAS and found their results to be reassuringly consistent with theoretical calculations.

“OAS analysis is very simple and very fast. Once you have data with coherent oscillations, it [takes] only a few minutes to generate OAS. The method also avoids assumptions about the oscillatory signals that are being induced. As a result, it can process complex chemical and material systems [information] very rapidly,” said author Matthew Kirschner.

OAS is scalable for especially complex or crowded spectra. As a result, it can help facilitate the design of systems by better understanding and even utilizing the phonon modes for functional nanomaterial applications.

The authors have made the code for OAS analysis accessible to the general public in order for widespread use and development. They expect their research to impact the design of materials for photo-switches, chemical sensors and non-linear optics.

Source: “Phonon-induced plasmon-exciton electronic coupling probed via oscillation-associated spectra,” by Matthew S. Kirschner, Yeonjun Jeong, Austin P. Spencer, Nicolas E. Watkins, Xiao-Min Lin, George C. Schatz, Lin X. Chen, and Richard D. Schaller, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5116836 .