The quantum sound of metals

Every musical instrument has its own sound with a frequency spectrum that is determined by the shape of the instrument. In analogy to that, every metal has its characteristic frequency spectrum reflecting the properties of its electrons. Our investigation of the quantum sound of electrons in the metal PdRhO2 shows that electrons move quickly in the crystallographic planes whereas they hardly move perpendicular to the planes. The quantum music sounds slightly differently than expected and will help understand the particular hydrodynamic transport properties of electrons in these metals.