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Résumé |
Thermal Hall conductivity has recently emerged as an
experimentally accessible property of insulating materials. Theoretical
understanding thereof has remained a challenge, in particular since the
breaking of time-reversal symmetry by neutral particles is nontrivial
and can emerge from multiple mechanisms (semiclassical dynamics,
skew-scattering, etc). In a first part, I will present a general
formulation of inelastic skew-scattering of energy-carrying bosons by
other collective excitations. Specializing to phonon-magnon
interactions, I will show that a phonon thermal Hall effect from
skew-scattering in antiferromagnets is allowed by magnetoelastic and
spin-orbit couplings. In a second part, I will focus on the free
semiclassical dynamics of neutral bosons, and present a systematic
derivation of their kinetic equation, incorporating the topological
dynamics of wavepackets in the form of Berry curvatures (generalized to
phase space). This makes it possible to treat inhomogeneous systems,
including boundaries, textures, etc., in a compact and natural manner. |
