Electrons found to flow like water
Science Magazine has published three back-to-back papers on an important discovery in solid state physics. Leiden physicist Jan Zaanen wrote a Perspective article on the subject in the same issue of 4 March.
Three separate research groups have simultaneously discovered that electrons behave like a fluid when flowing through certain materials. Until now, scientists had only observed this effect in extremely exotic circumstances, such as the conditions at the time of the Big Bang. It is the first time that physicists have seen electrons flowing as if they were a stream of water in ‘everyday’ materials—in this case graphene and PdCoO3.
If you turn on a garden hose, you do not just initiate a crossfire of individual water particles, but an actual stream of liquid water. Water is different from the sum of its parts. It behaves like a liquid, with phenomena like waves, turbulence and viscosity. Electricity, on the other hand, doesn't behave like a lliquid. When you switch on the lights, you only set in motion a series of single electrons, like bullets from a gun.
But the beauty of physics is that things often aren’t as normal as they seem at first sight. In three independent studies and using different materials, researchers found that electrons can actually mimic water. And astonishingly, they did so at practically the same time. When electrons form a strongly interactive system, they act collectively as a fluid, provided that temperatures are not close to absolute zero. As a leading expert in the field, Jan Zaanen has published a Perspective article on the discovery in Science.
Zaanen sees great potential in the richness of electron flows, compared to traditional electric currents. The shocks and turbulence that are inherent in so-called hydrodynamics might give future technology a whole new dimension. The finding is also significant for research. For example, it enables scientists to test their theories about the physics behind strange metals in the laboratory. These materials are made up of a vibrant soup of extremely interacting particles that scientists have very little knowledge about, and which will probably reveal fundamental laws of nature.