The “Sound” of Weyl Fermions

Heat in a solid is mainly carried by lattice vibrations (phonons) and conducting electrons. These mechanisms of heat conduction are so dominant over other forms that in an ordinary material they are often assumed to be the only ones that matter. But as reported in a pair of papers, an exotic “vibration” of electrons might provide a third, significant way to conduct heat at low temperatures [1, 2]. This effect occurs in a family of materials called Weyl semimetals [3, 4], and it might be harnessed to guide heat through a material.