#heat flow

Swapping one atom can cut heat flow through a molecule by half

Swapping a single atom can fine-tune the thermal conductance of single-molecule junctions without affecting their electrical conductance, according to a study led by University of Michigan Engineering with collaborators at the University of Augsburg published in Nature Materials. To study heat flow through single molecules, the researchers trapped a small organic molecule between two gold electrodes and systematically replaced one hydrogen atom with progressively heavier halogens: fluorine, chlorine, bromine and iodine. Each swap to a heavier atom resulted in further reduction of heat transport through the junction, which cuts heat flow in half upon iodine substitution. "This is a powerful demonstration that heat flow can be controlled with atomic precision—a capability that could transform how we design thermoelectric devices and molecular materials for thermal management," said Pramod Reddy, a professor of mechanical engineering and materials science and engineering at U-M and co-corresponding author of the study.

(Nanowerk News) Normally, a material absorbs and emits heat in a linked way: a surface that absorbs heat well at a certain wavelength and direction will also emit heat in the same ways. This fundamental relationship, known as reciprocity, limits our ability to independently control heat absorption and heat emission. But if absorption and emission could be separated, engineers could design devices that absorb heat from one direction while emitting it in another. By ‘steering’ thermal energy, they could create more efficient thermal management, energy conversion, infrared sensing, and thermal communication technologies.

Tiny silicon structures compute with heat, achieving 99% accurate matrix multiplication

MIT researchers have designed silicon structures that can perform calculations in an electronic device using excess heat instead of electricity. These tiny structures could someday enable more energy-efficient computation. In this computing method, input data are encoded as a set of temperatures using the waste heat already present in a device. The flow and distribution of heat through a specially designed material forms the basis of the calculation. Then the output is represented by the power collected at the other end, which is a thermostat at a fixed temperature. The researchers used these structures to perform matrix vector multiplication with more than 99% accuracy. Matrix multiplication is the fundamental mathematical technique machine-learning models like LLMs utilize to process information and make predictions.

This electric field trick boosted heat flow by nearly 300%

Scientists have discovered a surprisingly powerful new way to control how heat moves through solid materials using electricity.

Researchers at the Department of Energy's Oak Ridge National Laboratory (ORNL), working with The Ohio State University and Amphenol Corporation, have uncovered a surprising new way to control how heat moves through solid materials. Their findings challenge long held assumptions about heat transport and could lead to more efficient cooling systems, energy devices, and electronic technologies. Published in PRX Energy, the study found that applying an electric field to a specialized ceramic changes the behavior of phonons, the tiny atomic vibrations responsible for carrying heat. When the atoms vibrate in the same direction as the electric field (poling direction), those phonons persist much longer than vibrations moving across it. As a result, heat travels almost three times more efficiently along the direction of the electric field than it does in other directions. "Being able to control both how fast and in what manner heat flows could lead to devices that manage thermal energy far more efficiently," said Puspa Upreti, an ORNL postdoctoral research associate.

Metamaterials enable control of heat transfer at nanoscale, potentially transforming energy and electronics

Heat behaves in predictable ways: a hot cup of coffee cools, a laptop warms your hands, the sun heats Earth. But at scales thousands of times smaller than a human hair, those rules begin to break down, and scientists are learning how to take advantage of that. Engineered materials reshape heat transfer A new study, published in Nature from researchers at Carnegie Mellon University, in collaboration with Stanford University and Purdue University, shows that heat can be manipulated far more powerfully than previously demonstrated using carefully engineered metamaterials. The work offers one of the clearest experimental confirmations yet that heat transfer can be actively designed and enhanced.

Crystalline material conducts heat even worse than glass and water—and that's promising

A research team from Aarhus University, Denmark, has measured and explained the exceptionally low thermal conductivity of the crystalline material AgGaGe3Se8. Despite its ordered structure, the material behaves like a glass in terms of heat transport—making it one of the least heat-conductive crystalline solids known to date. At room temperature, AgGaGe3Se8 exhibits a thermal conductivity of just 0.2 watts per meter-Kelvin—which is three times lower than water and five times lower than typical silica glass. The material is composed of silver (Ag), gallium (Ga), germanium (Ge), and selenium (Se), and has previously been studied for its optical properties. Now, for the first time, researchers from iMAT—the Aarhus University Center for Integrated Materials Research—have measured its thermal transport properties and identified the structural origin of its unusually low thermal conductivity.

Current flows without heat loss in newly engineered fractional quantum material

A team of US researchers has unveiled a device that can conduct electricity along its fractionally charged edges without losing energy to heat. Described in Nature Physics, the work, led by Xiaodong Xu at the University of Washington, marks the first demonstration of a "dissipationless fractional Chern insulator," a long-sought state of matter with promising implications for future quantum technologies. From quantum Hall to fractional phases The quantum Hall effect emerges when electrons are confined to a two-dimensional material, cooled to extremely low temperatures, and exposed to strong magnetic fields. Much like the classical Hall effect, it describes how a voltage develops across a material perpendicular to the direction of current flow. In this case, however, that voltage increases in discrete, or quantized steps.