New theory transforms understanding of nanoscale heat transport

New theory transforms understanding of nanoscale heat transport
by Clarence Oxford
Los Angeles CA (SPX) Oct 07, 2025

Heat, once thought to flow smoothly and predictably through materials, behaves far more intricately when observed at the nanoscale. A team from Auburn University and the U.S. Department of Energy's National Renewable Energy Laboratory has now unveiled a unified statistical theory that reshapes how scientists understand and predict heat conduction at microscopic and ultrafast scales.

For centuries, Joseph Fourier's 19th-century diffusion law has guided how engineers model heat transfer - from engines to buildings. Yet as devices shrink to the nanometer level, that classical picture breaks down. In this regime, heat can ripple like a wave, carry memory of past states, or even flow ballistically, defying the smooth diffusion seen in macroscopic systems.

"Fourier's law was written 200 years ago; this breakthrough rewrites the rules for how heat conducts in the nanoscale and ultrafast world of today," said Prof. Jianjun (JJ) Dong, Thomas and Jean Walter Professor of Physics at Auburn University.

The new framework, detailed in Physical Review B, connects the atomic-scale vibrations that carry heat to all known transport regimes - from diffusive to ballistic - using a single, predictive model. Co-authored by Dong and Dr. Yi Zeng of NREL, the work unites decades of fragmented theories under one statistical foundation capable of explaining how heat behaves within complex nanostructures and across material interfaces.

Analogous to a city traffic system, the theory recognizes that energy flow depends on local "traffic" conditions: some regions move freely, others experience congestion or echo previous surges. This holistic approach enables accurate modeling of thermal dynamics in next-generation processors, semiconductors, and energy systems.

As devices continue to miniaturize, thermal management has become as critical as electronic performance. "Heat doesn't just disappear into the background - it's the hidden player that determines whether future technologies will run faster, cooler, and more sustainably," Dong noted.

Beyond electronics, the new model could influence the study of magnetic, spin, and electronic transport, offering insights for quantum computing materials and energy storage innovations. By redefining how scientists simulate and control heat, the Auburn-NREL collaboration bridges a 200-year gap between Fourier's law and the demands of 21st-century nanotechnology.

Research Report:Time-domain theory of transient heat conduction in the local limit