Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a solid-state refrigerator that uses quantum physics in micro- and nanostructures to cool a much larger object to extremely low temperatures, according to a company statement.
Previous devices using this cooling principle fell short of general-purpose refrigerators since they could not be coupled to arbitrary payloads. To create a viable refrigerator, researchers developed optimized NIS structures and techniques to couple such multiple structures to arbitrary objects.
Using three linked NIS devices, researcher were able to reduce the temperature of a 1.9 cm3 copper stage from 290 mK to 256 mK with 700 pW of cooling power at 290 mK. The researchers are planning to achieve base temperatures near 100 mK.
The cooling elements are sandwiches of a normal metal, a 1-nanometer-thick insulating layer, and a superconducting metal. When a voltage is applied, the hottest electrons “tunnel” from the normal metal through the insulator to a superconductor. The temperature in the normal metal drops dramatically and drains electronic and vibrational energy from the object being cooled.
Cooling to temperatures below 300 mK currently requires complex, large and costly apparatus. NIST researchers want to build simple, compact alternatives to make it easier to cool NIST’s advanced sensors. Researchers plan to boost the cooling power of the prototype refrigerator by adding more and higher-efficiency superconducting junctions, while building a more rigid support structure.
“It’s one of the most flabbergasting results I’ve seen,” project leader Joel Ullom says. “We used quantum mechanics in a nanostructure to cool a block of copper. The copper is about a million times heavier than the refrigerating elements. This is a rare example of a nano- or microelectromechanical machine that can manipulate the macroscopic world.”
The research, which has been published in the Applied Physics Letters, has been supported by NASA.