Scientists Created a New Kind of Metal Where Electrons Flow Like a Fluid

Simulation of colliding particles

Exploring a metal superconductor comprised of both Germanium and Niobium (NbGe2), Boston College Assistant Professor of Physics Fazel Tafti, along with colleagues from Florida State University and the University of Texas in Dallas, discovered that a strong interaction between phonons and electrons modify the transport of electrons from their typical, particle-like (or diffusive) motion, to a hydrodynamic, of fluid-like, motion. And this marks the first discovery of an electron-phonon liquid within the NbGe2 substance, said Tafti in an embargoed release shared with IE. "We wanted to test a recent prediction of the 'electron-phonon fluid'," he added in the release, emphasizing how phonons are a crystal structure's vibration. "Typically, electrons are scattered by phonons which leads to the usual diffusive motion of electrons in metals. A new theory shows that when electrons strongly interact with phonons, they will form a united electron-phonon liquid." 

In metals, electrons are normally expected to be diffusive in their movement, operating as individual particles – in other words, they don't gain momentum as a group. In a new study, scientists have now discovered a type of metal where electrons actually do flow in a fluid-like way – like water in a pipe – by interacting with quasiparticles called phonons, which emerge from vibrations in a crystal structure.

This causes the electrons to shift from diffusive (particle-like) to hydrodynamic (fluid-like) behavior in their movement. The metal superconductor that causes this behavior is a synthesis of niobium and germanium called ditetrelide (NbGe2), the research team reports. Potentially, it could give rise to a new type of electronic device. There's currently a lot of research interest in the idea of electron-phonon liquids, even if it's not fully clear yet what the implications might be for the electronic gadgets and communication systems of the future.

This new work opens up plenty of interesting options for future research. Next, the researchers want to find other materials that behave in the same way as NbGe2, and to work on controlling the fluid flow of electrons for future applications. "Whereas electron-phonon scattering relaxes the electron's momentum in metals, a perpetual exchange of momentum between phonons and electrons may conserve total momentum and lead to a coupled electron-phonon liquid," the researchers explain in their study.

"Such a phase of matter could be a platform for observing electron hydrodynamics."