T₁ Anisotropy Elucidates Spin Relaxation Mechanisms in an S = 1 Cr(IV) Optically Addressable Molecular Qubit
Abstract
Paramagnetic molecules offer unique advantages for quantum information science owing to their spatial compactness, synthetic tunability, room-temperature quantum coherence, and potential for optical state initialization and readout. However, current optically addressable molecular qubits are hampered by rapid spin–lattice relaxation (T₁) even at sub-liquid nitrogen temperatures. Here, we use temperature- and orientation-dependent pulsed electron paramagnetic resonance (EPR) to elucidate the negative sign of the ground state zero-field splitting (ZFS) and assign T₁ anisotropy to specific types of motion in an optically addressable S = 1 Cr(o-tolyl)₄ molecular qubit. The anisotropy displays a distinct sin²(2θ) functional form that is not observed in S = 1/2 Cu(acac)₂ or other Cu(II)/V(IV) microwave addressable molecular qubits. The Cr(o-tolyl)₄ T₁ anisotropy is ascribed to couplings between electron spins and rotational motion in low-energy acoustic or pseudoacoustic phonons. Our findings suggest that rotational degrees of freedom should be suppressed to maximize the coherence temperature of optically addressable qubits.
Copyright and License
© 2023 American Chemical Society.
Acknowledgement
The authors wish to acknowledge Dr. Paul H. Oyala for assistance with EPR spectroscopy and Dr. Erica Sutcliffe for helpful discussions. N.P.K. acknowledges support by the Hertz Fellowship. N.P.K. and K.M.L. both acknowledge support by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1745301. Financial support from the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Condensed Phase and Interfacial Molecular Science (DE-SC0022089) is gratefully acknowledged.
Contributions
N.P.K. and K.M.L. are co-first authors.
Conflict of Interest
The authors declare no competing financial interest.
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Additional details
- ISSN
- 1948-7185
- Hertz Foundation
- National Science Foundation
- DGE-1745301
- United States Department of Energy
- DE-SC0022089