Soutenance de Léo Mangeolle
| When |
Sep 19, 2022
from 04:00 to 06:00 |
|---|---|
| Where | Salle Condorcet (1 place de l'École) |
| Contact Name | Léo Mangeolle |
| Attendees |
Léo Mangeolle |
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This thesis focuses on the intrinsic scattering of phonons by a general quantum degree of freedom, i.e. a fluctuating field Q with a priori completely general correlations, constrained only by unitarity and translational invariance. The scattering rates induced by this interaction are computed using quantum scattering theory. The phonon non-equilibrium dynamics is studied via kinetic theory and Boltzmann’s equation.
The computed scattering rates involve two- and four-point correlation functions of the Q field. We obtain general and explicit forms for these correlations which isolate the contributions to the Hall conductivity. We then evaluate these correlation functions, and hence the thermal transport, in the case of a general interaction between one phonon and two free fields. We treat both the bosonic and the fermionic cases.
We then consider the illustrative example of an ordered two-dimensional antiferromagnet. In this case the Q field is the most general composite of two magnon operators arising from spin-strain coupling allowed by the symmetries. Thermal conductivity in this model is studied both analytically and numerically, and we show evidence of a non-vanishing phonon Hall effect.
So as to clarify the role of correlations in a magnetically disordered phase, we finally consider the case of a spinon Fermi surface U(1) spin liquid. In this case the Q field is a composite of two spinon operators. We propose a model of spin-phonon coupling which leads to non-vanishing thermal Hall conductivity.