A 30 mK, 13.5 T scanning tunneling microscope with two independent tips

Area of Science:

• Condensed Matter Physics
• Materials Science
• Low-Temperature Physics

Background:

• Advanced microscopy techniques are crucial for probing quantum materials.
• Ultra-low temperatures and high magnetic fields enable the study of exotic electronic states.
• Developing sophisticated instrumentation is key to overcoming experimental challenges in these regimes.

Purpose of the Study:

• To present the design, construction, and performance of a novel two-tip scanning tunneling microscope (STM).
• To demonstrate its capability for operation at ultra-low temperatures (30 mK) and high magnetic fields (13.5 T).
• To showcase its utility for in situ sample manipulation and high-resolution surface analysis.

Main Methods:

• Integration of a two-tip STM head within a dilution refrigerator.
• Development of an in situ sample transfer mechanism from ultra-high vacuum to the cryostat at 1.5 K.
• Implementation of vibration isolation and radio-frequency (RF)-filtered wiring for noise reduction.

Main Results:

• Demonstrated effective noise reduction through spectral current noise analysis and atomic resolution imaging.
• Verified high-field performance by observing the magnetic field dependence of the superconducting gap in CuxBi2Se3.
• Achieved an effective tip/sample temperature of approximately 184 mK, yielding an energy resolution of 16 μeV at 35 mK.

Conclusions:

• The developed two-tip STM is a highly capable instrument for ultra-low temperature and high-field research.
• The design facilitates detailed investigation of material properties at the nanoscale.
• The system provides excellent energy resolution for probing quantum phenomena in condensed matter systems.