Coherent Dynamics in Solutions of Colloidal Plexcitonic Nanohybrids at Room Temperature

Abstract

The increasing ability to prepare systems with nanoscale resolution and address their optical properties with ultrashort time precision is revealing quantum phenomena with tremendous potential in quantum nanotechnologies. Colloidal plexcitonic materials promise to play a pivotal role in this scenario. Plexcitons are hybrid states originating from the mixing of the plasmon resonances of metal nanostructures with molecular excitons. They allow nanoscale confinement of electromagnetic fields and the establishment of strong couplings between light and matter, potentially giving rise to controllable and tunable coherent phenomena. However, the characterization of the ultrafast coherent and incoherent dynamics of colloidal plexciton nanohybrids remains highly unexplored. Here, two dimensional electronic spectroscopy (2DES) is employed to study the quantum coherent interactions active after the photoexcitation of these systems. By comparing the response of the nanohybrids with the one of the uncoupled systems, the nonlinear photophysical processes at the base of the coherent dynamics are identified, allowing a step forward toward the effective understanding and exploitation of these nanomaterials.

Identification of Design Principles for the Preparation of Colloidal Plexcitonic Materials

“…ℏ γ and ℏk , instead, can be measured as the full width at half-maximum of the respective uncoupled plasmonic and excitonic peaks. It is worth noticing that CPMs, being prepared by wet chemistry methodologies, are intrinsically inhomogeneous samples, with distributions of NPs’ size and shape, thickness of the capping layer, number of coupled QEs, and so forth, which might slightly complicate the estimate of the Rabi splitting and coupling regime …”

“…22−26 More recently, several efforts were also paid to characterize and exploit their quantum properties, such as superfluidity, 27,28 superconductivity, 27,29 Bose−Einstein condensation, 30−32 and coherent behavior. 33,34 Polaritonic materials are essentially prepared with two classes of cavities: the Fabry−Peŕot (or planar) cavities and plasmonic cavities. In the first class, the light bounces back and forth between two parallel mirrors forming standing waves, whose fields are amplified.…”

“…Polaritonic materials are currently attracting considerable interest in several fields. For example, regarding chemistry applications, it was demonstrated that these polaritonic systems could be effectively employed to tune the rate of chemical reactions, , increasing the efficiency of molecular energy transfer, , or modifying the temporal and spatial propagation of the energy. − In addition, cavities small enough [such as plasmonic nanoparticles (NPs) or arrays] can confine the light below the diffraction limits, potentially unlocking an unprecedented capability of directing the migration of the excitation energy at the nanoscale. , They have also been proposed as suitable candidates for sensing, imaging, , and for different kinds of devices such as parametric amplifiers, OLED, and solar cells. − More recently, several efforts were also paid to characterize and exploit their quantum properties, such as superfluidity, , superconductivity, , Bose–Einstein condensation, − and coherent behavior. , …”

“…It is worth noticing that CPMs, being prepared by wet chemistry methodologies, are intrinsically inhomogeneous samples, with distributions of NPs' size and shape, thickness of the capping layer, number of coupled QEs, and so forth, which might slightly complicate the estimate of the Rabi splitting and coupling regime. 34 Plexciton Dataset. Even with the uncertainties related to the boundaries of the SC regime, the theoretical model discussed in the previous section clearly points out the main parameters controlling the coupling strength g and the Rabi splitting Ω R .…”

Ultrafast dynamics in plasmon–exciton core–shell systems: the role of heat

“…The strongly damped Rabi oscillations have been observed for surface plasmon polariton systems, 10 and only very recently, coherent dynamics have been observed in colloidal systems. 11…”