Phonon Angular Momentum in Magnetic Field · Hall Viscosity Tensor · Transverse Stress
Parameters
Phonon in B: Lattice ions in magnetic field gain Coriolis force F=qv×B, splitting degenerate phonon modes into chiral branches (left/right circularly polarized).
Hall viscosity: η_H = (ℏ/2)⟨L_z⟩ per unit cell — angular momentum per phonon × Bose occupation. Causes transverse stress response σ_xy ≠ σ_yx.
Topological: Chern numbers of phonon bands contribute to η_H. Related to Berry curvature in phonon BZ.