Instruments that can operate at extremely low temperatures and in ultra-high vacuum conditions are needed to better understand quantum phenomena such as superconductivity and superfluidity. In order to cool equipment to temperatures nearing absolute zero, researchers often utilize 3He–4He dilution refrigeration, but this requires continuous circulation of fluid, which can cause vibrations that interfere with highly sensitive observations. Researchers at Forschungszentrum Jülich have taken a new approach scanning tunneling microscopy (STM) for quantum physics research, constructing an STM that reaches millikelvin temperatures using a magnetic cooling system to reduce mechanical noise.
The research center’s new quantum microscope uses a cooling device based on the process of adiabatic demagnetization to reach temperatures as low as 30 millikelvin. Adiabatic demagnetization has been used to achieve extremely low temperatures since the 1930s and was the first technique used by scientists to reach temperatures below 1 Kelvin in the laboratory. However, Jülich physicists say they are the first to apply the refrigeration technique to cool an STM to millikelvin-range temperatures.
The Jülich microscope can operate nearly vibration-free and in ultra-high vacuum conditions. The instrument has no moving parts and the temperature is controlled by changing the strength of the electric current passing through an electromagnetic coil in the cooling device, said researcher Ruslan Temirov. The microscope’s modular design also allows for potential future upgrades to further advance its capabilities. The researchers presented their design in a paper published in the Review of Scientific Instruments.
“Adiabatic cooling is a real quantum leap for scanning tunneling microscopy. The advantages are so significant that we are now developing a commercial prototype as our next step,” said researcher Stefan Tautz.
The physicists hope to use the microscope to study quantum phenomena and materials that could lead to the development of new quantum technology like computers and sensors.
Photo: Researchers Stefan Tautz (left below), Taner Esat (left above) and Ruslan Temirov (right) at the Jülich quantum microscope. Credit: Sascha Kreklau/Forschungszentrum Jülich