Scientists have developed a new approach to cooling materials using a calorimetric scanning probe. Calorimeters measure the flow of heat. The experiment used a very small calorimeter, with a sensing area about the size of a human hair. In the past, scientists have used special lasers to cool atoms to really low temperatures. However, this new approach uses a simple LED to cool solid-state materials. By running the electrical current in the LED in the opposite direction than it normally moves, they could suppress how much heat the material gave off. The photons moved from the object to the LED, cooling the material.
These insights may enable future devices that use how light behaves at the nanometer scale for cooling. It could lead to new solid-state cooling devices that are as good as current solid-state refrigeration devices based on thermoelectrics (conversion of heat to electricity and vice versa). It also has the potential to cool future microelectronics. This technology is compatible with current ways to manufacture technologies that control, detect, and create light.
A known research technique to cool atoms to very low temperatures is using coherent laser radiation. Recent theory has suggested a different approach to cool solid-state materials – using a conventional light emitting diode (LED). For the first-time, experiments confirmed this concept. Scientists measured dramatically increased cooling rates using this technique. In the process, the density of photons in the diode dropped due to applied reverse bias, where electricity in the LED flows in a direction opposite to normal. The photons tunneled from the object to the LED, cooling the material. This demonstration of active cooling (refrigeration) via nanoscale effects established that there are novel opportunities for refrigeration at this length scale. The principles elucidated in this work are expected to advance research into nanophotonic cooling. Because this technology is compatible with current optoelectronic fabrication technologies, it has the potential for rivaling current state-of-the-art solid-state cooling technologies and on-chip cooling. Similar to the immense interest generated by thermoelectric materials for solid-state electronic refrigeration, this work is expected to be of significant interest to scientists and engineers.
University of Michigan
This research was supported by DOE-BES award (Scanning Probe Development and Analysis) and from the Army Research Office award (Instrumentation and Nanopositioning Tools).
L. Zhu, A. Fiorino, D. Thompson, R. Mittapally, E. Meyhofer, P. Reddy, “Near-field photonic cooling through control of the chemical potential of photons” Nature 566, 238 (2019). [DOI: 10.1038/s41586-019-0918-8]