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PhD: Saptam Ganguly

Directors: Prof. Gustau Catalán,Group Leader, Dr David Pesquera, Senior Postdoctoral Researcher and Dr Gabriele de Luca, Postdoctoral Researcher at Oxide Nanophysics Group at ICN2 .

Short Abstract: Light-matter interactions are ubiquitous in nature and play a pivotal role in understanding the functioning of the universe. In the context of solid state phsyics, this thesis explores three different aspects of light-matter interaction in three different oxides. The main theme being how photoexcited carriers in their excited state get affected by the crystal structure and conversely how they can affect the crystal structure during their lifetime. In the first case, in ferroelectric BiFeO3, it is shown how asymmetry of the crystal structure dictates charge carrier transport, resulting in first real time imaging of asymmetric charge transport in ferroelectric. In the second case, a converse effect, i.e., how the photoexcited electrons distort the crystal structure of prototypical ferroelectric BaTiO3 is shown. This effect is leveraged to photoactuate membrane resonators with large responses compared to non-ferroelectric ones. Finally, in the third case, in prototypical strongly correlated oxide VO2, the photoinduced phase transition is studied on ultrafast timescales with an objective to understand the effect of phase coexistence on the dynamics and pathways of transition. The insights gained from these experiments broaden the understanding of light-matter interaction in diverse material systems, specifically, mechanisms governing charge transport and structural response, and highlighting the potential for controlling material properties through optical excitation.