Hyperfine-Induced Asymmetric Overhauser Field in MAPbI₃ Thin Films.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Optics

Background:

• Metal halide perovskites are key in photovoltaics and optoelectronics.
• Understanding spin relaxation mechanisms is crucial for advanced functionalities.
• Spin-based optical applications require detailed knowledge of spin dynamics.

Purpose of the Study:

• To demonstrate dynamic nuclear polarization (DNP) in MAPbI3 films.
• To investigate the mechanisms of spin relaxation and coupling in perovskites.
• To explore nuclear-assisted control of spin coherence.

Main Methods:

• Dynamic Nuclear Polarization (DNP) experiments on polycrystalline MAPbI3 films.
• Measurement of Overhauser fields generated by electron-nuclear spin interactions.
• Analysis of DNP field orientation dependence to probe hyperfine asymmetry.

Main Results:

• Efficient DNP achieved via electron-hole spin flip-flop processes with nuclear spins.
• Significant Overhauser fields generated: up to 35 mT for 207Pb and 15 mT for 127I.
• Observed DNP field dependence on magnetic field orientation, indicating asymmetric hyperfine coupling.

Conclusions:

• Unveiled a novel regime of asymmetric hyperfine coupling in halide perovskites.
• Established strong coupling between electron/hole spins and nuclear spin baths (Pb and I).
• Provided a foundation for nuclear-assisted spin coherence control in solution-processed opto-spintronic materials.