Electrons found to flow like water (Perspective article in Science by Leiden PI Jan Zaanen)


Science Magazine publishes three back-to-back papers on an important discovery in solid state physics. Leiden physicist Jan Zaanen writes a Perspective article on the matter in the same issue of March 4th.

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, like the conditions at the time of the Big Bang. It is the first time that physicists see electrons flowing as if they were a stream of water in ‘everyday’ materials—in this case graphene and PdCoO3.

If you turn on a gardening hose, you not just initiate a cross fire of individual water particles, but an actual stream of liquid water. Water is different from the sum of its parts. It behaves as a liquid, with phenomena like waves, turbulence and viscosity. When switching on the lights, however, you only set in motion a series of single electrons, like bullets from a gun. Electricity normally doesn’t behave like a fluid.

But the beauty of physics is that things oftentimes 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 interaction 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 publishes 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 to so-called hydrodynamics might give future technology a whole new dimension. Also for research purposes the finding is of significant value. 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 probably will reveal fundamental laws of nature.