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Updated: May 9, 2026
10:40
High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy
Published on: June 28, 2016
Experimental Quantification of Spin-Phonon Coupling in Molecular Qubits Using Inelastic Neutron Scattering
Stefan H Lohaus1, Kay T Xia1, Yongqiang Cheng2
1Division of Chemistry and Chemical Engineering, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, United States.
Journal of the American Chemical Society
|May 8, 2026
Summary
Researchers developed an experimental method to link molecular structure and spin relaxation. This technique quantifies spin-phonon coupling (SPC) and reveals how molecular design impacts spin coherence times.
Area of Science:
- Quantum sensing
- Molecular magnetism
- Materials science
Background:
- Electronic spin states are sensitive to their environment, crucial for nanoscale sensing.
- Vibrational motion (phonons) limits spin coherence times in molecular systems.
- Understanding spin-phonon coupling (SPC) is key to controlling spin dynamics.
Purpose of the Study:
- To develop a fully experimental method for quantifying spin-phonon coupling (SPC) coefficients.
- To investigate the relationship between molecular structure, lattice dynamics, and spin relaxation.
- To identify vibrational modes that dominate spin relaxation in molecular spin systems.
Main Methods:
- Combined temperature-dependent inelastic neutron scattering (INS) for vibrational spectra.
- Measured spin relaxation rates using electron paramagnetic resonance (EPR).
- Applied the framework to copper(II) phthalocyanine (CuPc) and copper(II) octaethylporphyrin (CuOEP) molecular systems.
Main Results:
- Identified two distinct spin relaxation regimes dominated by different phonon energies.
- Observed significantly larger SPC coefficients for optical phonons (>185 cm⁻¹) above 40 K.
- Found that structural distortions in CuOEP reduce SPC, enabling room-temperature spin coherence.
Conclusions:
- Established a broadly applicable experimental method linking crystal structure, lattice dynamics, and spin relaxation.
- Demonstrated that molecular structure dictates spin-phonon coupling and spin coherence.
- Provided insights into designing molecular systems for enhanced spin coherence at higher temperatures.
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