Superconductor phase transitions manage radiative heat transfer - Michigan Engineering News
Summarize this article with:
February 2, 2026 February 2, 2026 Superconductor phase transitions manage radiative heat transfer A first-of-its-kind experiment finds niobium suppresses nanoscale radiative heat transfer when in a superconducting state, with implications for quantum computing. By: Patricia DeLacey Experts Pramod Sangi Reddy See full bio Professor of Mechanical Engineering and Materials Science and Engineering Yuxuan Luan See full bio Postdoctoral Fellow of Mechanical Engineering at the University of Michigan Edgar Meyhofer See full bio Professor of Mechanical Engineering When cooled to its superconducting state, niobium blocks the radiative flow of heat 20 times better than when in its metallic state, according to a study led by a University of Michigan Engineering team. The experiment marks the first use of superconductivity—a quantum property characterized by zero electrical resistance—to control thermal radiation at the nanoscale. Leveraging this effect, the researchers also experimentally demonstrated a cryogenic thermal diode that rectifies the flow of heat (i.e., the heat flow exhibits a directional preference) by as much as 70%.
This research was funded by the U.S. Department of Energy, Office of Naval Research and the National Science Foundation. “This work is exciting because it experimentally shows, for the very first time, how nanoscale heat transfer can be tuned by superconductors with potential applications for quantum computing,” said Pramod Sangi Reddy, a professor of mechanical engineering and materials science and engineering at U-M and co-corresponding author of the study published in Nature Nanotechnology. Managing heat in quantum computing Quantum computers could theoretically perform complex calculations in a few seconds that would take classical computers thousands of years, but quantum information is incredibly heat-sensitive. Because even a small amount of heat destroys quantum information, quantum computers operate at cryogenic temperatures close to absolute zero. Managing temperatures at the nanoscale is notoriously difficult. At this scale, the light-based quantum energy packets, called thermal photons (part of thermal radiation), tunnel across nanometer vacuum gaps. In a phenomenon known as near-field radiation, heat flows between objects at higher rates than the classic physics “blackbody limit.” This study marks the first exploration of superconductivity as a means to block near-field radiation. “This work, at its core, is exploring how energy is transported at the atomic and nanometer length scales. Since this is uncharted territory, I am truly excited to have made these measurements and obtained first data that describe these completely unexplored phenomena,” said Yuxuan Luan, a postdoctoral fellow of mechanical engineering at U-M and lead author of the study. A superconductor switch As the first investigation of its kind, the research team developed a new experimental platform and specialized calorimeter to study nanoscale heat transport at cryogenic temperatures. “Major advances in instrumentation and nanofabrication enabled us to develop highly sensitive calorimeters optimized for measurements at temperatures comparable to outer space and integrate them into an ultra-high vacuum instrument,” said Edgar Meyhofer, a professor of mechanical engineering at U-M and co-corresponding author of the study. The scanning calorimetric probe consists of a vertical cantilever integrated with a serpentine heater and a thermometer. A 50-micron diameter silica sphere, coated in gold, is attached to the tip. Within a cryostat, the researchers positioned the sphere on the tip of the calorimetric probe just 10 nanometers above a silicon nitride plate coated with a 200 nanometer-thick film of niobium. The gap is so small that it is narrower than the wavelength of thermal radiation and allows thermal photons to tunnel across to the niobium. A new experimental platform and specialized calorimeter allowed a University of Michigan Engineering-led team to study nanoscale heat transport at cryogenic temperatures. Hovering 10 nanometers above a plate, the calorimeter integrates a platinum line heater and thermometer into a cantilever attached to a silica sphere coated in gold. Below, the silicon nitride plate coated with a thin layer of niobium has a heater and thermometer attached. When cooled below 7.4 Kelvin, the niobium plate transitions to a superconducting state and blocks thermal radiation emitted from the gold sphere. Credit: Yuxuan Luan, University of Michigan Engineering. The switching behavior of the system hinges on niobium’s temperature-dependent superconductivity. Niobium behaves like a typical metal at most temperatures, but acts as a superconductor at temperatures approaching absolute zero. By using a heater below the niobium plate to vary the temperature above and below 7.4 Kelvin (-446 F), the researchers created a superconductor switch. Measuring the radiative heat transfer between the sphere and plate revealed a 20-fold suppression of heat transfer when niobium transitions to its superconducting phase. When niobium is a superconductor, the large energy gap prevents low-frequency thermal photons from the gold sphere from being absorbed by niobium. Next, by leveraging the superconducting phase transition of niobium, the researchers demonstrated a cryogenic thermal diode with heat rectification as high as 70% for near-field thermal radiation—the highest reported for photonic thermal diodes. Looking ahead, the new approach could be the key for more stable quantum architectures. It offers a completely new approach for controlling heat currents and holds promise for applications in thermal management of superconducting devices, including in novel quantum computers that employ superconductors. The research is funded by the U.S. Department of Energy Basic Energy Sciences from the Scanning Probe Microscopy Division (DESC0004871), the U.S. Office of Naval Research (N00014-24-1-2132) and the National Science Foundation (CBET 2232201). Researchers from Stanford University also contributed to the study. The device was built in the Lurie Nanofabrication Facility and studied at the Michigan Center for Materials Characterization, both of which are operated and maintained with support from indirect cost allocations in federal grants. ALTMETRIC ATTENTION SCORE Study: A cryogenic near-field thermal diode leveraging superconducting phase transitions Related Stories February 2, 2026 Superconductor phase transitions manage radiative heat transfer A first-of-its-kind experiment finds niobium suppresses nanoscale radiative heat transfer when in a superconducting state, with implications for quantum computing. September 22, 2025 U-M quantum testbed enables remote experiments The optical fibers connecting two quantum research labs at the University of Michigan mark the first piece of a local quantum network and remote user test facility. September 19, 2025 Quantum chemistry: Making key simulation approach more accurate Density functional theory is limited by a mystery at its heart: the universal exchange-correlation functional. U-M researchers are trying to uncover it.