Friday March 11th, 2022 in Hand 1144

Abstract: Two-dimensional Ruddlesden-Popper metal halides (2D-RPMHs) are materials composed of quasi-2D layers of metal-halide octahedra separated by long (~1nm) organic cationic layers. The latter facilitate electron and hole quantum confinement within the metal-halide layers resulting in a quantum-well like structure. Properties of excitons (electron-hole bound states) in such structures are characterized by strong binding energy (>200 meV) arising from the dynamically screened Coulomb interactions. We have experimentally observed that polaronic effects arising from the lattice dressing of the carriers, are not only active but that they fundamentally define excitons in 2D-RPMHs. We thus refer to such excitons as the exciton-polarons, with properties that are measurably distinct than those of free excitons in semiconductors. In this talk, I will discuss the quantum dynamics of exciton-polarons and provide spectroscopic insights into the peculiar phonon-phonon, exciton-phonon and exciton-exciton interactions. I will present our perspective on how the coherent optical response of 2D-RPMHs can be effectively rationalized within the “exciton-polaron” framework, in which lattice dressing of photo-carriers constitute an integral component of excitonic wavefunction, with consequences on exciton recombination dynamics and diffusion.

Bio: Dr Ajay Ram Srimath Kandada received his PhD in Physics from Politecnico di Milano, Italy in 2013 for his work on ultrafast spectroscopy of organic photovoltaic materials. He subsequently moved to the Italian Institute of Technology as a post-doctoral researcher to investigate the excited state dynamics and defect physics of bulk metal-halide perovskites. In 2016, he received the Marie Sklodowska Curie global fellowship from the European Commission to implement advanced optical spectroscopies at University of Montreal (Canada), Georgia Institute of Technology (USA) and at the Italian Institute of Technology (Italy). He was appointed as Adjunct Assistant Professor at Wake Forest University in 2020 and later as tenure-track Assistant Professor in 2022. His research interests include electronic and optical properties of emerging semiconductors probed by nonlinear ultrafast spectroscopy and quantum-optical methods.

Please join us for a reception with Dr. Kandada at 3:00 pm in Hand 1134.
Hosted by Dr. Mahesh Gangishetty