Charge and energy transfer in large molecular assemblies: Quantum state diffusion with an adaptive basis

Area of Science:

• Quantum mechanics
• Molecular physics
• Computational chemistry

Background:

• Understanding excitation energy transfer (EET) in molecular aggregates is crucial for designing artificial photosynthetic systems and organic electronics.
• The dynamics of EET are often complicated by environmental interactions leading to decoherence.
• Simulating these processes in large systems is computationally challenging.

Purpose of the Study:

• To evaluate the suitability of the stochastic, wave-function based quantum state diffusion (QSD) approach for simulating excitation dynamics in large molecular aggregates.
• To investigate the complex regime where excitation transfer times are comparable to decoherence times.

Main Methods:

• Employed the quantum state diffusion (QSD) approach, a stochastic wave-function method.
• Utilized an adaptive basis set to efficiently represent the evolving quantum state.
• Simulated the motion of an excitation in large molecular aggregates under realistic environmental conditions.

Main Results:

• Demonstrated that the QSD approach combined with an adaptive basis is well-suited for numerical treatment of excitation dynamics.
• Successfully captured the complex interplay between transfer and decoherence in large molecular systems.
• The method proved effective even when transfer and decoherence timescales are comparable.

Conclusions:

• The stochastic QSD method with an adaptive basis provides a robust numerical tool for studying excitation dynamics in complex molecular aggregates.
• This approach enables accurate simulations in challenging regimes previously difficult to model.
• The findings support the use of QSD for advancing research in areas like light-harvesting systems.