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Bridging Vibrations and Spins: Mode-Resolved Spin-Phonon Coupling Revealed through THz EPR/Magnetic IR Simulation
Haowei Chen1, Maurice van Gastel1, Alexander Schnegg2
1Department of Molecular Theory and Spectroscopy, Max-Planck-Institut für Kohlenforschung, Kaiser Wilhelmplatz 1, 45470 Mülheim an der Ruhr Germany.
The Journal of Physical Chemistry. A
|February 10, 2026
Summary
Researchers developed a simulation protocol to measure spin-phonon coupling in molecular qubits using THz EPR/Magnetic IR spectroscopy. This method provides direct experimental insights into quantum coherence limitations.
Area of Science:
- Quantum Information Science
- Molecular Magnetism
- Spectroscopy
Background:
- Molecular electron spin qubits offer potential for quantum technologies but face coherence limitations due to spin-phonon coupling.
- Understanding spin-phonon coupling is vital for improving qubit performance, yet experimental insights are scarce.
- Vibrational spectroscopy under magnetic fields presents a promising avenue for studying these interactions.
Purpose of the Study:
- To develop and validate a comprehensive simulation protocol for extracting spin-phonon coupling parameters.
- To demonstrate the utility of Terahertz Electron Paramagnetic Resonance (THz EPR) and Magnetic Infrared (IR) spectroscopy for probing spin-phonon interactions.
- To elucidate the dominant spin-phonon coupling mechanisms in a model molecular system.
Main Methods:
- Development of a simulation protocol to analyze THz EPR/Magnetic IR spectra.
- Application of a one-phonon model to interpret spectral features, including weak coupling regimes.
- Validation of the simulation protocol using a tetrahedral high-spin Cobalt(II) complex.
- Benchmarking simulation results against quantum-chemical calculations.
Main Results:
- The study presents the first comprehensive simulation protocol for extracting spin-phonon coupling from THz EPR/Magnetic IR spectra.
- The method successfully identified a dominant spin-phonon coupling attributed to a twisting vibrational mode in the Co(II) complex.
- Excellent agreement was achieved between experimental data, simulation results, and quantum-chemical computations.
Conclusions:
- THz EPR/Magnetic IR spectroscopy serves as a powerful direct probe for spin-phonon coupling.
- The developed simulation protocol enables accurate characterization of spin-phonon interactions in molecular systems.
- This work advances the understanding of coherence limitations in molecular spin qubits and guides future qubit design.
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