Accurate quantum dynamics of electronic excited states is essential for meaningful description of various non-equilibrium charge and energy transfer processes. One of the most popular schemes to study quantum dynamics is the semiclassical trajectory surface hopping method developed by Tully. Despite its popularity and high precision, the method fails to describe many intrinsically quantum phenomena, such as super-exchange, Auger-type processes, uncertainty principle and electronic decoherence. This limitation is related to the way the nuclear wavepacket is represented – via a swarm of uncorrelated trajectories.<br/>In this presentation, I will report a novel semiclassical method for description of non-adiabatic electronic dynamics. The method, called second-quantized surface hopping (SQUASH), generalizes Tully’s trajectory hopping to the space of many-particle states that introduce entanglement and correlation of nuclear trajectories, by construction. The framework of second quantization, known in the field of many-body physics, is adopted. The second quantization is applied to many-(quasi)particle states, in which each (quasi)particle is associated with a nuclear trajectory. The method allows coupling between individual semiclassical trajectories via energy flow and common phase evolution. By construction, the method captures fundamental properties of a proper quantum wavepacket, such as branching, uncertainty principle, and electronic decoherence.<br/>As a first application, the method is used to model superexchange process that occurs during multiple exciton generation in semiconductor quantum dots and singlet fission in molecular crystals. The transition of electron between the initial and final states involves intermediate states. In the superexchange regime, in which the intermediate states are higher in energy than the initial and final states, the standard Tully surface hopping fails. In contrast, the SQUASH method fixes this shortcoming, giving excellent agreement with the exact result. The agreement is achieved while retaining the simplicity and efficiency of trajectory surface hopping method.<br/>

Second-quantized surface hopping

249th National Meeting (2015)

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