At the nanoscale of today’s most cutting-edge semiconductors, a phonons don’t remove enough heat. That’s why Purdue University researchers are focused on opening a new nanoscale lane on the heat transfer highway by using hybrid quasiparticles called “polaritons.”
Thomas Beechem loves heat transfer. He talks about it loud and proud, like a preacher at a big tent revival.
“We have several ways of describing energy,” said Beechem, associate professor of mechanical engineering. “When we talk about light, we describe it in terms of particles called ‘photons.’ Heat also carries energy in predictable ways, and we describe those waves of energy as ‘phonons.’ But sometimes, depending on the material, photons and phonons will come together and make something new called a ‘polariton.’ It carries energy in its own way, distinct from both photons or phonons.”
Like photons and phonons, polaritons aren’t physical particles you can see or capture. They are more like ways of describing energy exchange as if they were particles.
Polaritons have been used in optical applications—everything from stained glass to home health tests. But their ability to move heat has largely been ignored, because their impact becomes significant only when the size of materials becomes very small. “We know that phonons do a majority of the work of transferring heat,” said Jacob Minyard, a Ph.D. student in Beechem’s lab.
“The effect of polaritons is only observable at the nanoscale. But we’ve never needed to address heat transfer at that level until now, because of semiconductors.”
Source: Journal of Applied Physics, Purdue University, Phys.org