The excitation of matter by light underlies some of the most important human-made technologies, and processes in nature. The dynamics of the photoexcited state is modulated by the motion of the environment which can successfully steer it to a desired state, or alternatively destroy it before it can be converted to useful energy. The BATH project strives to recover the information on the system-bath interaction using two-dimensional electronic spectroscopy (2DES). This technique is the most sophisticated third-order time resolved technique providing detailed information on the dynamics of electronic excitation on a sub-20fs timescale.
The work preferentially focuses on materials incorporating both plasmonic nanoparticles and molecular aggregates. From a fundamental standpoint they can exhibit quantum interferences, and have a complex dissipative environmental bath consisting of molecular vibrations, solvent motion and phonon modes of the lattice. In addition, many-body effects (e-e scattering) influence the early dynamics. From a practical standpoint, plasmon-based materials are candidates for quantum optics manipulations (cavity quantum electrodynamics, adiabatic passage methods, coherent population trapping) as well as photocatalysis (plasmon enhanced photochemistry). They are thus an ideal problem to answer fundamentally important questions with very realistic applications.
The work is arranged into two mutually supporting directions. We carry out spectroscopy experiments (pump-probe, 2DES) on plasmon-based materials to reveal their dissipative mechanisms and identify the features of the 2DES spectrum which can be directly associated to system-bath couplings. We also develop the theory to understand the photoexcited dynamics using simple models that can be solved analytically, and carry out simulations of the 2DES experiment.
