Interplay between Magnetoresistance and Kondo Resonance in Radical Single-Molecule Junctions.

Area of Science:

• Molecular electronics
• Quantum transport phenomena
• Organic radical chemistry

Background:

• Single-molecule junctions are crucial for molecular electronics.
• The Kondo effect and magnetoresistance (MR) are key quantum phenomena in such systems.
• Understanding spin-dependent transport in organic molecules is an active research area.

Purpose of the Study:

• To investigate the transport properties of tunable single-molecule junctions.
• To explore the relationship between the Kondo effect, magnetoresistance, and molecular structure.
• To determine the origin of high magnetoresistance in organic perchlorotrityl radical junctions.

Main Methods:

• Fabrication and low-temperature electrical transport measurements of single-molecule junctions.
• Utilizing gold electrodes for contact with perchlorotrityl radical molecules.
• Mechanical tuning of junction length via stretching.

Main Results:

• Observed zero-bias anomalies characteristic of the Kondo effect in some junctions.
• Measured significant magnetoresistance (MR), which was stronger in junctions lacking Kondo resonance.
• Demonstrated tunability of the MR amplitude by mechanically stretching the junctions.
• Attributed high MR to spin-dependent scattering at the metal-molecule interface.

Conclusions:

• The Kondo effect in these junctions originates from the unpaired spin of the perchlorotrityl radical.
• High magnetoresistance is primarily an interference effect involving spin-dependent scattering.
• Mechanical stretching offers a method to tune the magnetoresistance of single-molecule junctions.