University of Basel’s Professor Dominik Zumbühl and colleagues have succeeded in magnetically cooling a nanoelectronic device to a temperature of 2.8 mK (millikelvin).
“Magnetic cooling is based on the fact that a system can cool down when an applied magnetic field is ramped down while any external heat flow is avoided,” the researchers said.
“Before ramping down, the heat of magnetization needs to be removed with another method to obtain efficient magnetic cooling.”
“This is how we succeeded in cooling a nanoelectronic chip to a temperature of 2.8 mK, thereby achieving a new low temperature record.”
Professor Zumbühl and co-authors used a combination of two cooling systems, both of which were based on magnetic cooling.
They cooled all of the chip’s electrical connections to temperatures of 150 μK (microkelvin).
They then integrated a second cooling system directly into the chip itself, and also placed a Coulomb blockade thermometer on it.
The construction and the material composition enabled them to magnetically cool this thermometer to a temperature of 2.8 mK.
“The combination of cooling systems allowed us to cool our chip down to below 3 mK, and we are optimistic than we can use the same method to reach the magic 1 mK limit,” Professor Zumbühl said.
“It is also remarkable that we are in a position to maintain these extremely low temperatures for a period of seven hours,” the scientists said.
“This provides enough time to conduct various experiments that will help to understand the properties of physics close to absolute zero.”
The research is published in the journal Applied Physics Letters.
M. Palma et al. 2017. On-and-off chip cooling of a Coulomb blockade thermometer down to 2.8 mK. Appl. Phys. Lett 111, 253105; doi: 10.1063/1.5002565