Scientists Detect Exciton in Metal, Gain Clues How Light Is Transformed into Energy
3 June 2014
The fundamental quasi-particle that is formed in the interaction between light and matter in metals, exciton, has been detected for the first time by scientists from the University of Pittsburgh and Institute of Physics in Zagreb.
By experimenting with silver crystals, the research team discovered that their surface can maintain the state of excitons 100 times longer than most metals. This allowed the scientists to capture and study the elusive particles using a newly developed multi-dimensional coherent spectroscopic technique.
Excitons are particles of light-matter interaction that usually exist in metals for no longer than approximately 100 attoseconds (0.1 quadrillionth of a second). Their short lifespan is the reason why light reflected by metals is an almost perfect replica of the original - thus providing the foundation for all kinds of optical communication, as well as for the natural process of photosynthesis. It is also the reason why scientists so far have failed to capture and study them.
The breakthrough may lead scientists to finally understand the quantum mechanical processes behind the seemingly mundane everyday phenomenon of light being reflected by a metal surface. What was known so far is that when an electromagnetic field, such as light, hits a metal mirror, it excites the surface's free electrons and a consequent acceleration creates the reflection.
Even though scientists have understood the input and output mechanics of the process for a while, they've lacked the exact knowledge about the quantum mechanics of the light exciting the electrons. Now, with the ability to detect excitons in metals, scientists can find out how light is converted into energy and control the process of reflection, opening the door for metals to be used as active elements in optical communications.