Lessons on electronic decoherence in molecules from exact modeling.

Area of Science:

• Quantum mechanics
• Molecular dynamics
• Condensed matter physics

Background:

• Electronic decoherence is typically modeled using approximate system-bath interactions.
• Existing models often neglect explicit quantum mechanical treatment of both electronic and nuclear degrees of freedom.

Purpose of the Study:

• To develop and apply an exact quantum mechanical method for simulating electronic decoherence dynamics.
• To investigate fundamental mechanisms of electronic coherence loss in molecular systems.
• To provide a benchmark for testing approximate decoherence models.

Main Methods:

• Employed an exact method treating electronic and nuclear degrees of freedom quantum mechanically.
• Utilized the Jordan-Wigner transformation for fermionic operators.
• Applied the discrete variable representation for nuclear operators.
• Simulated dynamics of a model many-body molecular system (Su-Schrieffer-Heeger Hamiltonian with Hubbard interactions).

Main Results:

• Demonstrated electronic decoherence is possible even with a one-dimensional nuclear bath.
• Showed that decreasing bath mass generally accelerates electronic decoherence.
• Found electron-electron interactions significantly impact decoherence in non-pure-dephasing dynamics.
• Validated classical bath models for short-time decoherence dynamics.
• Identified conditions for the relevance of separable initial superpositions in decoherence studies.

Conclusions:

• The exact simulation method provides a standard for validating approximate decoherence models.
• Fundamental insights into electronic decoherence mechanisms were gained, unachievable with approximate methods.
• The findings offer a framework for interpreting and modeling coherence phenomena in molecules.