To examine the behavior and chemistry of the new liquid, a small crystal of the material is mounted on a device. The inset shows the atomic structure of the material. Credit: Fazel Taffti, Boston College
The Boston College team has created a new metal specimen that allows electron motion to flow in the same manner water does in a pipe. This is according to Nature Communications.
Fazel Tafti, an assistant professor of Physics at Boston College, discovered that the interaction between electrons, phonons, and electrons in the superconductor metal, a synthesis of Niobium, Germanium, and Florida State University, alters the transport of electrons. This is called the hydrodynamic or fluid-like regime.
Tafti stated that the findings are the first to be made of an electron-phonon fluid inside NbGe 2.
Tafti stated that they wanted to test a prediction of an 'electron phonon fluid'. He noted that phonons refers to vibrations in a crystal structure. "Typically electrons are scattered through phonons, which leads to the diffusive motion that electrons in metals. New theory suggests that electrons can interact strongly with phonons to form an electron-phonon liquid. This liquid will flow within the metal in exactly the same manner as water does in a pipe.
The discovery of the material will be a catalyst for further exploration and application of the material by Taftiworking together with Professor of Physics Kenneth Burch of Boston College, Luis Balicas from FSU and Julia Chan of UT-Dallas.
Tafti observed that water flows in pipes, and electrons flow in wires. Although they sound similar, these phenomena are fundamentally different. Hydrodynamic laws govern water molecules and they flow as a fluid continuum. However, electrons flow as particles and are diffused inside metals by lattice vibrations.
Hung-Yu Yang was a graduate student researcher who received his doctorate in BC in 2021. His contributions to the team's investigation were significant. They focused on conduction of electricity within the new metal, NbGe 2.
Three experimental methods were used: Raman scattering revealed a shift in the vibration of NbGe 2 crystals due to special electron flow; electrical resistivity measurements revealed a higher than expected mass for electrons; X-ray difffraction revealed the material's crystal structure.
Researchers used a technique called "quantum oscillations" for evaluating the mass electrons within the material. They found that the mass electrons in all trajectories was three-fold higher than expected, according to Tafti. His work is supported by National Science Foundation.
Tafti stated, "This was really surprising because we didn't expect such 'heavy electrons" in a seemingly straightforward metal." We eventually realized that heavy electron behavior was due to strong electron-phonon interactions. The strong interaction of electrons with lattice vibrations or phonons makes them 'dragged' through the lattice, making it appear that they have gained mass and are heavy.
Tafti stated that the next step will be to discover other materials within this hydrodynamic regime using the electron-phonon interactions. His team will also be focusing on the control of the hydrodynamic fluid electrons in these materials and engineering new electronic gadgets.
Continue reading Researchers modify the interaction of electrons within an atomically thin solid
More information: Evidence for a coupled electron-phonon fluid in NbGe 2, Nature Communications (2021). Information from Nature Communications Evidence of a Coupled Electron-phonon Liquid in NbGe (2021). DOI: 10.1038/s41467-021-25547-x
