Researchers at the Oak Ridge National Laboratory, Institut Néel in France, Aalto University in Finland, SUNY University at Buffalo in the US, and Johannes Kepler University in Austria have discovered a new kind of density wave in fermion liquids. Fermions are part of a group of particles, including protons, neutrons, and electrons, and they all obey the Pauli Exclusion Principle. The principle states that no two fermions can exist in the same energy state, which makes the interplay between particles in a fermion liquid very difficult to model.
The researchers shot neutrons at an atom-thick layer of helium-3, a rare isotope of helium. This two dimensional setup allowed the researchers to observe a wave not seen before in three dimensional systems, or not seen for long. Zero-sound oscillations like this are often damped out in three dimensional systems, but they may be of great importance to high-temperature superconductivity.
Some researchers believe it is high frequency density oscillations that cause high-temperature superconductivity. To test this, the team plans on repeating the experiment with an electron liquid, instead of a helium-3 liquid. Even if it turns out there is no connection between the waves and superconductivity, this discovery could greatly improve our understanding of other quantum fluids and many-body physics, which controls the makeup of metals.