While studying a material that could help unlock the secrets of superconductors, scientists have accidentally discovered a “demon” particle that was first theorized almost 70 years ago, but had never been experimentally confirmed.
Electrons are strange particles. When they travel through solids, their interactions with each other can form collective excitations that function like entirely new particles with different characteristics. These are known as quasiparticles.
A particular form of quasiparticle, called a plasmon, occurs due to plasma oscillations, and these have a new charge and mass separate from the electrons that make them up. However, plasmons were thought to be impossible at room temperature because energy levels are inadequate for the masses required to form them.
But in 1956, theoretical physicist David Pines predicted an exception to the rule – electrons in multiple energy bands could group together in an out-of-phase pattern, forming a plasmon that has no mass or charge. Without any mass they can form at any energy level, and therefore any temperature. This theoretical particle became known as “Pines’ demon,” and has eluded detection ever since – at least, until now.
Scientists at the University of Illinois Urbana-Champaign and Kyoto University have now made the first direct detections of the demon in a metal called strontium ruthenate. The key, it turns out, was to not even be looking specifically for it.
“The vast majority of experiments are done with light and measure optical properties, but being electrically neutral means that demons don’t interact with light,” said Peter Abbamonte, lead author of the study. “A completely different kind of experiment was needed.”
PERCEPTION RESET 