Published 2024-02-01
“…Thus, in this limit, we should always be able to calculate the damping rate of thermal phonons by applying Fermi’s golden rule to the Hamiltonian H3 of cubic phonon-phonon coupling taken from quantum hydrodynamics, at least in the case of a convex acoustic branch and in the collisionless regime (where the eigenfrequency of the considered phonons remains much greater than the gas thermalization rate). Using the
many-body Green’s function method, we predict that, unexpectedly, this is not true in two dimensions, contrary to the three-dimensional case. …”
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