Spin waves in quasiequilibrium spin systems

Phys Rev Lett. 2006 Jul 28;97(4):047204. doi: 10.1103/PhysRevLett.97.047204. Epub 2006 Jul 28.

Abstract

Using the Landau Fermi liquid theory we discovered a new propagating transverse spin wave in a paramagnetic system which is driven slightly out of equilibrium without applying an external magnetic field. We find a gapless mode which describes the uniform precession of the magnetization in the absence of a magnetic field. We also find a gapped mode associated with the precession of the spin current around the internal field. The gapless mode has a quadratic dispersion leading to a T3/2 contribution to the specific heat. These modes significantly contribute to the dynamic structure function.