Conductance and Kondo effect in a controlled single-atom contact

Area of Science:

• Surface Science
• Condensed Matter Physics
• Quantum Phenomena

Background:

• The Kondo effect describes the interaction between magnetic impurities and conduction electrons in metals.
• Understanding single-atom properties is crucial for nanoscale electronics and quantum computing.

Purpose of the Study:

• To investigate the influence of a scanning tunneling microscope (STM) tip in contact with individual cobalt atoms on their electronic properties.
• To measure changes in the Kondo temperature (TK) of cobalt atoms when interacting with the STM tip.

Main Methods:

• Utilized a low-temperature scanning tunneling microscope (STM) to probe individual cobalt atoms adsorbed on a Cu(100) surface.
• Performed spectroscopy in the contact regime, transitioning from tunneling to direct tip-atom contact.
• Conducted theoretical calculations to model the electronic interactions.

Main Results:

• Observed a smooth transition from tunneling to contact regime at a conductance of approximately G0.
• Spectroscopy revealed a significant change in the Kondo temperature (TK) of cobalt atoms upon tip contact.
• Calculations confirmed that tip proximity shifts the cobalt d-band, influencing TK.

Conclusions:

• The electronic environment of single cobalt atoms is highly sensitive to the presence of the STM tip.
• Tip-atom interactions can be used to tune quantum phenomena like the Kondo effect at the atomic scale.
• This work provides insights into controlling single-atom properties for future nanoelectronic devices.