In metals, electrons are usually expected to be diffuse in their motion, functioning as individual particles, i.e., not gaining momentum as a group.
In a new study, scientists have now discovered a type of metal where electrons flow similarly to a fluid, such as water in a pipe, by interacting with quasiparticles called phonons, which come out of the vibrations of a structure. crystalline.
This causes electrons to move from diffusive (particle-like) behavior to hydrodynamic (fluid-like) behavior in their motion.
The metallic superconductor that causes this behavior is a synthesis of niobium and germanium called ditetrelide (NbGe2), according to the research team. Potentially, it could lead 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.
“Electrons are usually dispersed by phonons, which leads to the usual diffuse movement of electrons in metals. A new theory shows that when electrons interact strongly with phonons, they will form a united electron-phonon liquid. This new liquid will flow to the inside of the metal in exactly the same way that water flows through a pipe. “
(Fazel Tafti, Boston College)
At the top: a small crystal of the new material of a device, with the insert showing the atomic arrangement.
Three experimental methods confirmed the electron photon fluid hypothesis developed by Tafti and colleagues. The first was the measurement of the electrical resistivity of the metal, which showed that its electrons had a mass greater than normally expected.
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 greater than it should be, demonstrated a material mapping approach known as quantum oscillations – another sign that electrons and phonons were causing unusual behavior.
“That was really amazing because we didn’t expect‘ such heavy electrons ’in a seemingly simple metal,” Tafti says.
“Finally, we understood that the strong electron-phonon interaction was responsible for the behavior of heavy electrons. Because electrons interact with lattice vibrations, or phonons, they are strongly” dragged “by the lattice and it seems as if they have gained too much and get heavy. “
There is currently great interest in research into the idea of electron-phonon liquids, although it is not yet entirely clear what the implications may be for the electronic devices and communication systems of the future.
This new work opens up many interesting options for future research. The researchers then want to find other materials that behave in the same way as NbGe2 and work on controlling the flow of electron fluid for future applications.
“While the electron-phonon scattering relaxes the electron impulse in metals, a perpetual impulse exchange between phonons and electrons can preserve the total momentum and lead to an electron-phono coupled liquid,” the researchers explain. in his study.
“This phase of matter could be a platform for the observation of electronic hydrodynamics.”
The research has been published in Communications on Nature.