Mechanically Stable Kondo Resonance in an Organic Radical Molecular Junction

Area of Science:

• Molecular spintronics
• Organic radical chemistry
• Quantum transport phenomena

Background:

• Organic radicals possess intrinsic magnetic moments, low spin-orbit coupling, and weak hyperfine interactions, making them suitable for molecular spintronics.
• Nitronyl nitroxide radicals (NNRs) are a class of organic radicals with potential applications in spintronic devices.

Purpose of the Study:

• To investigate the charge transport properties of two NNR isomers with different backbone configurations (para and meta).
• To compare the electronic behavior of para-NNR and meta-NNR under varying temperature conditions.

Main Methods:

• Utilized a mechanically controlled break junction setup for charge transport measurements.
• Performed experiments at both room temperature and low temperature (6 K).
• Analyzed differential conductance to identify transport signatures like Kondo resonance.

Main Results:

• Para-NNR exhibited a clear Kondo resonance at 6 K, indicative of strong electron correlation effects.
• Meta-NNR did not display a Kondo resonance under the same experimental conditions.
• The Kondo peak in para-NNR showed a constant width, suggesting asymmetric coupling to the electrodes.

Conclusions:

• The backbone configuration of NNRs significantly influences their charge transport characteristics and the emergence of quantum phenomena like the Kondo effect.
• Asymmetric coupling between the radical molecule and the electrodes plays a crucial role in the observed transport properties.
• These findings contribute to the understanding of radical-based molecular spintronics and device design.