Efficient calculation of open quantum system dynamics and time-resolved spectroscopy with distributed memory HEOM (DM-HEOM).

Time- and frequency-resolved optical signals provide insights into the properties of light-harvesting molecular complexes, including excitation energies, dipole strengths and orientations, as well as in the exciton energy flow through the complex. The hierarchical equations of motion (HEOM) provide a unifying theory, which allows one to study the combined effects of system-environment dissipation and non-Markovian memory without making restrictive assumptions about weak or strong couplings or separability of vibrational and electronic degrees of freedom. With increasing system size the exact solution of the open quantum system dynamics requires memory and compute resources beyond a single compute node.

Modeling of Transient Absorption Spectra in Exciton-Charge-Transfer Systems.

Time-resolved spectroscopy provides the main tool for analyzing the dynamics of excitonic energy transfer in light-harvesting complexes. Inferring the time scales and effective coupling parameters from experimental data requires the development of numerically exact theoretical models. The finite duration of the laser-molecule interactions and the reorganization process during the exciton migration affect the location and strength of spectroscopic signals.

Laser pulse induced transient currents in a molecular junction: Effects of plasmon excitations of the leads.

The transient response of a molecular junction excited by a single laser pulse or by a sequence of pulses is studied theoretically utilizing a density matrix description. The approach focuses on the sequential transmission regime and accounts for intramolecular vibrations and vibrational relaxation. Besides the optical excitation of the molecule, also the laser pulse action on the leads is considered.

Photoinduced dynamics in a molecule metal nanoparticle complex: mean-field approximation versus exact treatment of the interaction.

Photoexcitation of a molecule placed in the proximity of a metal nanoparticle (MNP) is described theoretically. For a sufficient small spatial extension of the whole system the molecule-MNP coupling is given by the instantaneous Coulomb-interaction. The coupling can also be considered in terms of a local field to which an external field has been transferred due to the presence of the MNP.

Supramolecular complex coupled to a metal nanoparticle: computational studies on the optical absorption.

Absorption spectra of a supramolecular complex (SC) placed in the proximity of a spherical metal nanoparticle (MNP) are computed. A description of the absorption is used that is based on a density matrix propagation. The applied density matrix theory starts from a microscopic model including the Coulomb interaction between the SC and the MNP.

Photoinduced switching of the current through a single molecule: effects of surface plasmon excitations of the leads.

The photoinduced switch of the current through a single molecule is studied theoretically by including plasmon excitations of the leads. A molecule weakly linked to two spherical nanoelectrodes is considered resulting in sequential charge transmission scheme. Taking the molecular charging energy (relative to the equilibrium lead chemical potential) to be comparable to the molecular excitation energy, an efficient current switch in a low voltage range becomes possible.