PULLMAN, Wash. – Quite by accident, Washington State University researchers have achieved a 400-fold increase in the electrical conductivity of a crystal simply by exposing it to light. The effect, which lasted for days after the light was turned off, could dramatically improve the performance of devices like computer chips.
WSU doctoral student Marianne Tarun chanced upon the discovery when she noticed that the conductivity of some strontium titanate shot up after it was left out one day. At first, she and her fellow researchers thought the sample was contaminated, but a series of experiments showed the effect was from light.
“It came by accident,” said Tarun. “It’s not something we expected. That makes it very exciting to share.”
The phenomenon they witnessed—“persistent photoconductivity”—is a far cry from superconductivity, the complete lack of electrical resistance pursued by other physicists, usually using temperatures near absolute zero. But the fact that they’ve achieved this at room temperature makes the phenomenon more immediately practical.
And while other researchers have created persistent photoconductivity in other materials, this is the most dramatic display of the phenomenon.
The research, which was funded by the National Science Foundation, appears this month in the journal Physical Review Letters ( via news.wsu.edu ).