This book presents a theoretical study of the generation and conversion
of phonon angular momentum in crystals.
Recently, rotational motions of lattice vibrations, i.e., phonons, in
crystals attract considerable attentions. As such, the book
theoretically demonstrate generations of phonons with rotational
motions, based on model calculations and first-principle calculations.
In systems without inversion symmetry, the phonon angular momentum is
shown to be caused by the temperature gradient, which is demonstrated in
crystals such as wurtzite gallium nitride, tellurium, and selenium using
the first-principle calculations. In systems with neither time-reversal
nor inversion symmetries, the phonon angular momentum is shown to be
generated by an electric field. Secondly, the book presents the
microscopic mechanisms developed by the author and his collaborator on
how these microscopic rotations of nuclei are coupled with electron
spins. These predictions serve as building blocks for spintronics with
phonons or mechanical motions.