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High-Frequency Tails in Spectral Densities
Roman Korol1, Xinxian Chen1, Ignacio Franco1,2
1Department of Chemistry, University of Rochester, Rochester, New York 14627, United States.
The Journal of Physical Chemistry. A
|April 4, 2025
Summary
Accurately modeling open quantum systems requires a precise spectral density (SD). Capturing the full SD magnitude is crucial for reliable decoherence dynamics, especially for electronic relaxation rates.
Area of Science:
- Quantum dynamics
- Chemical physics
- Computational chemistry
Background:
- Numerically exact quantum dynamics methods are advancing for open systems.
- Path-integral, hierarchical equations of motion, and quantum analog simulators rely on the spectral density (SD).
- Focus is on decoherence dynamics of electronically excited species in solution where nonradiative relaxation dominates.
Purpose of the Study:
- Investigate the sensitivity of computed relaxation rates to spectral density (SD) representations.
- Address the challenge of accurately capturing the full spectral density magnitude for quantum simulations.
- Provide a method to recover correct relaxation rates in simulations with SD limitations.
Main Methods:
- Analysis of decoherence dynamics in electronically excited species.
- Comparison of different spectral density (SD) representations (e.g., Drude-Lorentz, Brownian modes).
- Development of a transformation to correct relaxation rates for limited SD representations.
Main Results:
- Computed relaxation rates are highly sensitive to the choice of SD representation and strategy.
- Electronic relaxation is dominated by high-frequency SD tails, which are orders of magnitude weaker than main features.
- Accurate SD representation over several orders of magnitude is necessary for correct early and late-time decoherence dynamics.
Conclusions:
- Accurate spectral density (SD) characterization is critical for reliable quantum dynamics simulations.
- A simple transformation can improve relaxation rate accuracy in simulations with constrained SDs.
- Findings facilitate comparison of simulation methods and enhance analog quantum simulations.
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