Experts have demonstrated a state that has so far been predicted only theoretically, in which electrons flow through a pipe through a pipe. As a working group around Hung-Yu Yang from the Boston College reports in "Nature Communications", the exotic liquid arises when electrons change heavily with the lattice vibrations of the material and retain their entire energy released from them. Under these conditions, they form a liquid together with the vibration quanta referred to as phonons. This means that the electrons no longer move as individual particles, but in a common state that is described by hydrodynamic equations.
So far, the detection of the predicted liquid has failed due to the fact that no material has the necessary combination of properties in superconductivity. In order for electrons and phonons to couple to each other, certain other interactions, for example scattering processes of the electrons between each other, must become very low. This is the case in the examined material NbGe2. Under these conditions, something strange happens: although the electrons continue to transmit their momentum to the phonons of the lattice vibrations during scattering processes, these are in turn scattered to the electrons and transmit the momentum back. As a result, the momentum circulates between electrons and phonons without losses, and instead of a movement of individual particles determined by scattering and diffusion, a flowing material is now observed.
The team around Yang showed the existence of the exotic fluid based on three differences to classic supercorders. On the one hand, the effective mass of the electrons proved to be three times as high as expected, which is due to the fact that the phonons contribute to the mass thanks to the coupling; On the other hand, the electrical properties of the material had changed. Finally, scatter experiments with infrared radiation show that the material swings differently than one would expect in the case of classic superconduct. This is a result of the hydrodynamic behavior of the electrons, which differs drastically from the classic movement scattered particles. Now the working group wants to check whether the superconductor behaves differently if its diameter is a few nanometers - comparable to water that flows through an ever closer tube.
