Primary thermometry triad at 6 mK in mesoscopic circuits

Area of Science:

• Quantum physics
• Mesoscopic electrical circuits
• Low-temperature physics

Background:

• Quantum phenomena are best observed at reduced temperatures.
• Mesoscopic circuits are ideal for exploring quantum behavior, but electron cooling is a significant challenge.
• Micrometre-scale devices are difficult to thermalize below 10 mK due to strong coupling to measurement lines and weak coupling to the substrate.

Purpose of the Study:

• To demonstrate electronic quantum transport at ultra-low temperatures (6 mK) in micrometre-scale mesoscopic circuits.
• To establish reliable thermometry methods for these extreme conditions.
• To overcome the limitations of electron cooling in mesoscopic devices.

Main Methods:

• Utilized a standard cryogen-free dilution refrigerator in a vacuum environment.
• Implemented and compared three in situ primary thermometers based on different physical principles: quantum shot noise, quantum back action of a resistive circuit, and conductance oscillations of a single-electron transistor.
• Focused on micrometre-scale mesoscopic circuits.

Main Results:

• Successfully demonstrated electronic quantum transport at 6 mK.
• Validated thermometry methods through inter-comparison of three distinct primary thermometers.
• Covered a broad spectrum of mesoscopic phenomena using the combined thermometry techniques.

Conclusions:

• Achieved quantum transport in mesoscopic circuits at 6 mK, significantly below the typical 10 mK limit.
• The developed thermometry approach is robust and applicable across various mesoscopic phenomena.
• This work paves the way for exploring quantum physics in the sub-millikelvin range with further advancements in thermalization and refrigeration.