Enhancing Coherence with a Clock Transition and Dynamical Decoupling in the Cr₇Mn Molecular Nanomagnet

Area of Science:

• Quantum computing
• Molecular spintronics
• Solid-state physics

Background:

• Molecular magnets offer tunable properties for spin qubits.
• Clock transitions (CTs) enhance coherence times (T2) by minimizing magnetic field sensitivity.
• Understanding decoherence mechanisms is vital for advancing molecular spin qubits.

Purpose of the Study:

• Investigate coherence times (T2) of Cr7Mn molecular nanomagnets near a zero-field clock transition (CT).
• Explore decoherence sources and mechanisms affecting molecular spin qubits.
• Develop a model to explain observed decoherence and electron-spin-echo envelope modulation (ESEEM) phenomena.

Main Methods:

• Utilized Hahn-echo and CPMG pulse sequences for coherence time measurements.
• Studied Cr7Mn variants at temperatures ≤2 K near a zero-field CT.
• Analyzed electron-spin-echo envelope modulation (ESEEM) oscillations and their dependence on experimental conditions.

Main Results:

• Achieved coherence times (T2) of ~1 μs at the CT and up to ~3.6 μs in the ESEEM regime.
• Demonstrated that decoherence and ESEEM are largely independent of molecular dilution and solvent deuteration.
• Observed that decoherence arises from internal molecular sources, including field fluctuations and transverse anisotropy (E) noise.

Conclusions:

• Coherence preservation mechanisms in molecular magnets are complex and molecule-intrinsic.
• The developed decoherence model, incorporating nuclear Larmor frequency noise and 1/f noise in E, accurately explains experimental observations.
• Findings provide crucial insights for the rational design of robust molecular-based spin qubits.