Strong light-matter coupling
The chemical and physical properties of molecular materials depend on weak and strong matter-matter interaction of their constituents. For example, gaseous He-atoms turn into liquid at very low temperature due to weak London dispersion forces, whereas, strong electrostatic interactions of Na+ and Cl- ions create an ionic crystal at room temperature. These interactions are operated by fluctuation of the electric field of the associated atoms or molecules in the system. A similar scenario can be drawn in light-matter interactions in which a photon (light) interact with a two level molecular state (fluctuating electronic cloud) and modify their properties by weak or strong interactions. As shown in the schematic above, under strong coupling (SC), the properties of the system are no longer purely those of the molecular constituents as they are modified by the appearance of new hybrid states generated by the molecule – vacuum field interactions. Coherence and tunability of energy levels are two other benefit of such hybridization. SC is typically achieved by placing an absorber in a resonant Fabry-Perot cavity under the right conditions.
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Our group activities can be broadly divided under the umbrella of chemistry (Polaritonic chemistry) and material science (Polaritronics).
Two of the main projects are given below.
Polaritonic chemistry
Strong coupling of photon to a vibrational transition should affect chemistry because it offers a simple way to modify a given chemical bond and hence their reactivity landscape - Polaritonic chemistry (Fig. 1). Very recently we experimentally proved that a ground state chemical reaction can be catalyzed (cavity catalysis) by coupling molecular vibrations to vacuum electromagnetic field at room temperature. The focus of the current study is to understand in depth the influence of vibrational strong coupling (VSC) on the chemical reactivity of molecules to determine the underlying principles, to make it as a novel and useful tool for chemists.
Polaritronics
In this project, efforts will be made to study electron/energy transfer processes mediated by extended nature of the polaritonic states of electronically and vibrationally coupled systems-Polaritronics (Fig. 2). Here, more emphasis will be given for improving the efficiency of transport in molecular materials, both electron and energy transfer rates via the polaritonic states. Quantum nature of light is being used here and hence the hybrid (light-matter) states inherit the properties. We are currently developing quantum sensors and phototransistors based on polaritonic states.
