A basic idea of college physics is that as pressure increases, so does thermal conductivity (a material’s ability to conduct heat).
Over a century of research has confirmed this rule. However, engineers have now discovered an exception.Applying strong pressure to boron arsenide, a recently discovered semiconducting material, increases its thermal conductivity. decreasedFindings described in . Naturecould challenge established theories and upend current models of how matter behaves under extreme conditions.
“Now that we’ve made this initial discovery, we don’t think it’s the only material that exhibits anomalous behavior,” said senior author of the study, Yongjie, a chemist and mechanical engineer at the University of California, Los Angeles. Hu said. If other materials exhibit this property, “the established understanding of thermal conductivity may be incorrect.”
In previous work, Hu and others confirmed that boron arsenide has a very high thermal conductivity. The scientist also calculated that the conventional thermal conductivity rule may not apply in certain situations.
To test these predictions, Hu and his colleagues placed a small piece of boron arsenide less than 100 microns thick in the gap between two diamonds. They applied pressure to the diamond sandwich to exert forces on the boron arsenide hundreds of times greater than those on the ocean floor. The researchers used ultrafast optics, spectroscopy and X-rays to record how the thermal conductivity of boron arsenide begins to decrease as heat propagates through the sample and strong pressure is applied. Did. They observed that the reduction in heatwaves is due to similar types of heatwaves overlapping and canceling each other out. This is a phenomenon predicted by quantum mechanics.
If Fu and his colleagues can show that this behavior generalizes to other materials, physicists will be able to modify established models for environments such as outer space, including Earth, and the interior of planets. said it might be necessary. The latter may change projections about climate change. This is because terrain temperatures are affected by what is happening inside the Earth.
The new study provides “the first and best experimental evidence I know that thermal conductivity can be tuned,” says UC Berkeley geophysicist Raymond Jeanloz. He was not involved in this research. The discovery “opens the door” for advanced techniques to cool electronics, saving energy by controlling thermal conductivity, he adds.
