Scientists have created a new type of metal where electrons flow like a fluid

In metals, electrons are normally expected to be diffusive in their motion, functioning as individual particles – in other words, they don’t pick up speed as a group.

In a new study, scientists have now discovered a type of metal in which electrons actually flow fluidly – like water in a pipe – interacting with quasi-particles called phonons, which emerge from vibrations in a crystalline structure.

This changes electrons from diffusive behavior (like particles) to hydrodynamic behavior (like a fluid) in their motion.

The metallic superconductor that causes this behavior is a synthesis of niobium and germanium called ditetrelide (NbGe2), the research team reports. Potentially, this could give birth to a new type of electronic device.

“We wanted to test a recent prediction of ‘electron-phonon fluid’,” says experimental physicist Fazel Tafti of Boston College.

Generally, electrons are dispersed by phonons, which leads to the usual scattering motion of electrons in metals. A new theory shows that when electrons strongly interact with phonons, they form a united electron-phonon liquid. liquid will flow inside metal in exactly the same way water flows in a pipe. “

(Fazel Tafti, Boston College)

Above: A small crystal of the new material on a device, with the inset showing the atomic arrangement.

Three experimental methods confirmed the electron-photon fluid hypothesis developed by Tafti and his colleagues. The first was the measurement of electrical resistivity in the metal, which showed that its electrons had a higher mass than one would normally expect.

Second, Raman scattering laser analysis showed that the vibration of NbGe2 changed due to the unusual flow of electrons, and finally x-ray diffraction techniques revealed the crystal structure of the metal.

The mass of electrons was three times larger than it should be, a material mapping approach known as quantum oscillations has shown: another sign that electrons and phonons were causing unusual behavior.

“It was really surprising because we weren’t expecting ‘such heavy electrons’ in a seemingly simple metal,” says Tafti.

“Eventually, we understood that the strong electron-phonon interaction was responsible for the behavior of heavy electrons. Because electrons strongly interact with lattice vibrations, or phonons, they are ‘dragged’ by the lattice and it seems that they have gained in mass and become heavy. “

There is currently a lot of research interest in the idea of ​​electron-phonon liquids, although it is not yet entirely clear what the implications might be for electronic gadgets and communication systems of the future.

This new work opens up many interesting options for future research. Next, the researchers want to find other materials that behave similarly to NbGe2, and work on controlling the fluid flow of electrons for future applications.

“While electron-phonon scattering relaxes the momentum of the electron in metals, a perpetual momentum exchange between phonons and electrons can conserve total momentum and lead to an electron-phonon coupled liquid. “, explain the researchers in their study.

“Such a phase of matter could be a platform for observing the hydrodynamics of electrons.”

The research was published in Nature Communication.