An Atomic-Scale Vector Network Analyzer

Area of Science:

• Condensed Matter Physics
• Nanotechnology
• Quantum Electronics

Background:

• Electronic devices are shrinking to atomic scales, operating at GHz frequencies.
• Conventional test equipment like vector network analyzers (VNAs) struggle to keep pace with atomic-scale device performance.

Purpose of the Study:

• To implement VNA capabilities at the atomic scale using a scanning tunneling microscope (STM).
• To exploit nonlinearities in atomic and nanostructure voltage-current characteristics for high-resolution microwave spectroscopy.
• To enable quantitative characterization of atomic-scale electronic properties at GHz frequencies.

Main Methods:

• Utilizing a scanning tunneling microscope (STM) for atomic-scale measurements.
• Employing phase-resolved microwave spectroscopy at GHz frequencies.
• Analyzing nonlinearities in voltage-current characteristics of atoms and nanostructures.
• Performing accurate de-embedding of transmission lines and applying distortion-corrected waveforms within the tunnel junction.

Main Results:

• Achieved VNA capabilities on the atomic scale.
• Determined amplitude and phase response up to 9.3 GHz with unprecedented spatial resolution.
• Quantitatively characterized the complex-valued admittance of individual magnetic iron atoms.
• Observed a lowpass response in iron atoms with a magnetic-field-tunable cutoff frequency.

Conclusions:

• The developed atomic-scale VNA technique enables precise characterization of nanoscale electronic components.
• This method provides new insights into the GHz frequency behavior of individual magnetic atoms.
• The magnetic-field tunability of the cutoff frequency opens avenues for novel spintronic devices.