Chiral Phonons and Electrical Resistivity of Ferromagnetic Metals at Low Temperatures

Ferromagnetism is an exciting phase of matter exhibiting strongly correlated electron behavior and a standard example of spontaneously broken rotational symmetry: below the Curie temperature, atomic magnets in an isotropic single-domain ferromagnetic metal align along a spontaneously chosen direction. The scattering of conduction electrons from thermal perturbations to this spin order, together with electron-electron collisions, mark the material electrical behavior at low temperatures, where the resistivity varies mostly quadratically with the temperature. Around liquid-helium temperatures however, an interesting phenomenon occurs, giving rise to an extra linear contribution to the variation of the electrical resistivity with temperature, whose theoretical explanation has encountered problems for a long time. Here, a spin-flip scattering mechanism of conduction electrons in ferromagnetic metals is introduced which arises from their interaction with the internal magnetic induction and is mediated by chiral modes of the crystal lattice vibrations carrying spin 1. This mechanism is able to explain the above anomaly and give a good account of the spin-lattice relaxation times of iron, cobalt and nickel at room temperatures.