Heat emission from hot bodies, in the form of electromagnetic radiation, is a well-known phenomenon utilized in various technologies such as light bulbs and night vision cameras. Traditionally, heat is expected to flow from warmer to cooler bodies. However, a pioneering study led by Professor Alejandro Manjavacas from the University of New Mexico's Physics and Astronomy department challenges this notion, particularly in the context of rotating nanostructures. This discovery holds significant potential for advancements in thermophotovoltaic energy generation and the thermal management of electronic devices.
The research, titled "Control of the Radiative Heat Transfer in a Pair of Rotating Nanostructures," was published in the journal Physical Review Letters. Collaborating with Manjavacas was Juan R. Deop-Ruano from the Institute of Optics in Madrid, Spain. Their study demonstrates that the radiative heat transfer between two rotating nanostructures can be precisely controlled - enhanced, diminished, or even reversed - by altering their rotation frequencies.
This breakthrough provides a novel method for manipulating radiative heat transfer through the rotation of nanostructures. "Our main discovery is that rotation can significantly alter the radiative heat transfer between two nanostructures," Manjavacas explained. "Without rotation, this transfer is solely dependent on the temperatures of the nanostructures. However, with rotation, the transfer can be increased, decreased, or even reversed."
Radiative heat transfer between material structures arises from thermal fluctuations in the electromagnetic field. When the distance between these structures is considerably smaller than the wavelength of thermal radiation, the radiative heat transfer can surpass the predictions of Planck’s Law due to near-field electromagnetic components. If the structures' dimensions also fall within this range, their electromagnetic resonances further amplify the transfer.
Applications and Technological Implications
Manjavacas underscored the potential applications of this research: "Any fundamental advancement in understanding radiative heat transfer can enhance technologies that rely on it." Notable examples include thermophotovoltaic energy generation and the nanoscale thermal management of electronic devices. As electronics continue to evolve, transistors in microchips are reaching nanoscale sizes, presenting significant cooling challenges. A deeper understanding of radiative heat transfer offers new mechanisms for heat extraction, paving the way for more efficient cooling technologies.
Manjavacas stressed the importance of controlling radiative heat transfer: "Developing new methods to control radiative heat transfer is essential for addressing technological challenges related to heat management and energy production. For instance, thermophotovoltaic energy generation involves converting heat into electromagnetic radiation, which is then absorbed by photovoltaic cells to produce electricity. Enhanced control over radiative heat transfer can significantly improve the efficiency of this process."
Future Research Directions
Looking forward, scientists are exploring several potential continuations of this work, including the conversion of heat into motion. "We are interested in investigating the possibility of turning heat into motion by exploiting Casimir interactions," Manjavacas noted. "Another intriguing avenue is to examine the interplay between rotation and magneto-optical responses in the context of radiative heat transfer and Casimir torque."
This research received support from the MCIN/AEI of Spain, the U.S. National Science Foundation, and a 2022 Leonardo Grant for Researchers in Physics from the BBVA Foundation.