Angular Momentum of Phonons and Einstein-de Haas Effect

ORAL

Abstract

We study angular momentum of phonons in a magnetic crystal. In the presence of a spin-phonon interaction, we obtain a nonzero angular momentum of phonons, which is an odd function of magnetization. At zero temperature, phonon has a zero-point angular momentum besides a zero-point energy. With increasing temperature, the total phonon angular momentum diminishes and approaches to zero in the classical limit. The nonzero phonon angular momentum can have a significant impact on the Einstein-de Haas effect. To obtain the change of angular momentum of electrons, the change of phonon angular momentum needs to be subtracted from the opposite change of lattice angular momentum. Furthermore, the finding of phonon angular momentum gives a potential method to study the spin-phonon interaction. Possible experiments on phonon angular momentum are also discussed.

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Authors

  • Lifa Zhang

    University of Texas at Austin

  • Qian Niu

    University of Texas at Austin, UT Austin, Department of Physics, University of Texas at Austin, University of Texas at Austin, Austin, Texas 78712, USA, The University of Texas at Austin, Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA