What They Say
Scientists at the US Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have published a paper via Nature that describes how the group has used lasers to stimulate quantum dots and captured images using a high speed ‘electron camera’ (MeV-UED) to watch the emissions. The experiments revealed that the incoming high-energy laser light ejects electrons from the dot’s atoms, and their corresponding holes – empty spots with positive charges that are free to move around – become trapped at the surface of the dot, producing unwanted waste heat.
In addition, electrons and holes recombine in a way that gives off additional heat energy. This increases the jiggling of the dot’s atoms, deforms its crystal structure and wastes even more energy that could have gone into making the dots brighter.
When hit with green light, the dots relaxed, and excited pairs of electrons and holes converted virtually all of the incoming energy to light. But when hit with purple light, some of the energy was trapped on the surface of the dot; this distorted the arrangement of surrounding atoms and wasted energy as heat. The results have broad implications for developing future quantum and photonics technologies where light replaces electrons in computers and fluids in refrigerators.
What We Think
I’m obliged to Stanford University for flagging this one up! I check the titles of articles in Nature, but I didn’t spot the significance of the article at the time! (BR)
