Impact of Vibrational Modes in the Plasmonic Purcell Effect of Organic Molecules

Abstract

By means of quantum tensor network calculations, we investigate the large Purcell effect experienced by an organic molecule placed in the vicinity of a plasmonic nanostructure. In particular, we consider a donor-π bridge-acceptor dye at the gap of two Ag nanospheres. Our theoretical approach allows for a realistic description of the continua of both molecular vibrations and optical nanocavity modes. We analyze both the ultrafast exciton dynamics in the large Purcell enhancement regime and the corresponding emission spectrum, showing that these magnitudes are not accurately represented by the simplified models used up to date. Specifically, both the two-level system model and the single vibrational mode model can only reproduce the dynamics over short time scales, whereas the Fermi’s golden rule approach accounts only for the behavior at very long times. We demonstrate that including the whole set of vibrational modes is necessary to capture most of the dynamics and the corresponding spectrum. Moreover, by disentangling the coupling of the molecule to radiative and nonradiative plasmonic modes, we also shed light into the quenching phenomenology taking place in the system.

Efficient Interlayer Exciton Transport in Two-Dimensional Metal-Halide Perovskites.

“…The influence of such non-equilibrium dynamics is expected to effectively shift the emission frequency towards the absorption band in the dielectric function of PbI4. 45 To estimate this effect, we plot the energy transfer rate obtained from Eq. ( 1) as a function of the emission frequency in Figure 3C.…”

A theoretical perspective on molecular polaritonics

“…In the context of molecular polaritonics, they have been shown to allow the descrip- tion of several molecules coupled to complex environments. [99][100][101] A fully converged tensor network calculation gives exact results, but becomes computationally challenging when long propagation times are desired as the entanglement grows over time. Furthermore, the formally infinite chain has to be truncated at finite length in any realistic calculation, with the required length increasing with propagation time (to prevent unphysical reflections from the end of the chain).…”

“…The molecular vibrations are then represented by an independent chain of harmonic oscillators. [99][100][101] Alternatively, the bath of harmonic vibrational modes can be represented through its correlation function and simulated using the time-evolving matrix product operator (TEMPO) method. 123,124 This uses a tensor network to describe the system's history over a finite memory time and can thus represent non-Markovian dynamics.…”

Theoretical Challenges in Polaritonic Chemistry

“…7,8,16,126 For high-dimensional nuclear wave functions, the method of choice is the Multiconfigurational Time-Dependent Hartree (MCTDH) algorithm, 127,128 possibly in its multilayer implementation. 129 When potential surfaces can be approximated as harmonic oscillators, tensor network approaches are another powerful way to perform full quantum dynamics 130,131 As a hallmark feature, methods relying on wavepacket propagations guarantee a correct dynamics of the nuclear wavepacket at both electronic and polaritonic avoided crossings, conical intersections, and seams between the PoPESs, including a correct decay of nuclear coherence without needing to resort to artificial corrections as in the semiclassical methods. Secondly, its propagation allows to exactly include decay channels in the dynamics, either through effective non-Hermitian Hamiltonians 11,12,83 that are exact when the dynamics after decay are not of interest, or by direct solution of a Lindblad-style master equation.…”