The electron-phonon interactions play very crucial role in determining the electrical and thermal properties of materials and importantly it is believed that these electron-phonon interactions are also responsible for superconductivity. It is well known that the Raman line shape and line width has information of phonon-phonon and electron-phonon interactions and till date very few efforts were made to separate out these contributions. During my presentation at SVVV I will touch upon the our recent methodologies for quantitative estimation of electron-phonon coupling (EPC) for each phonon mode taking base from second-order correction in polaron-energy resulting bandgap renormalization of the semiconductor by treating EPC as perturbation. This gives coupling constant (α_p) for the p^th phonon mode evident from the ex-pression: is phonon frequencyandisrenormalizationin the bandgap due to EPC. Similar result is also earlier observed. These theoretical inferences are experimentally explored using combination of optical absorption and Raman spectros-copies for ᴦ-phonons of temperature-varied GaN and TiO₂; results reveal a systematic enhancement in α_p with temperature that exhibits unique percent variation of α_p for each mode. A higher percent change is observed for the mode known to exhibit greater coupling strength, thereby supporting the theoretical discussions. The significance of this method is that it probes quantum level phonon-specific interactions with electrons which are otherwise probed with much advanced techniques. Furthermore, the quantitative approach for separation of phonon-phonon and electron phonon interactions will be presented.

Semiconductor, Raman Specrocopy, Optical Absorption