  Understanding the spectral and temporal dynamics of charge transfer plasmon
resonances that emerge in conductively connected plasmonic nanoparticles is
crucial for exploiting their potentials for enhanced infrared spectroscopy and
optical computing. In this article, we present a theoretical study based on
classical electromagnetism to describe the spectral signature and dephasing
time of charge transfer plasmons. By fitting the scattering curves and
near-field amplitude oscillations, we determine the spectral linewidth and
lifetime of charge transfer plasmons in conductively connected gold nanodisk
dimers. We find that, compared with the well-known particle plasmons and dimer
plasmons, charge transfer plasmons have a longer lifetime, which can be further
extended by manipulating the geometric parameters of nanojunction and
nanoparticles. Moreover, quantitative analyses of the optical near-field
amplitude reveal that charge transfer plasmon modes oscillate completely out of
phase with particle plasmon and dimer plasmon modes. The dephasing time and
charge transfer rate are found to be on a few femtosecond timescale, implying
that conductively connected plasmonic nanoparticles hold great promise as
channels for coherent transfer of energy and information in future all-optical
computing devices.
