arXiv:2108.04264 · Physical review. B./Physical review. B

Nonequilibrium scalar field dynamics starting from Fock states: Absence of thermalization in one-dimensional phonons coupled to fermions

Md Mursalin Islam, Rajdeep Sensarma

Published Jul 15, 2022• 8 citations

Abstract

We propose a method to study nonequilibrium dynamics of scalar fields starting from non-Gaussian initial conditions using Keldysh field theory. We use it to study dynamics of phonons coupled to noninteracting bosonic and fermionic baths starting from initial Fock states. We find that in one dimension long-wavelength phonons coupled to fermionic baths do not thermalize at low and high bath-temperatures. At low temperature, constraints from energy-momentum conservation lead to a narrow bandwidth of particle-hole excitations and the phonons effectively do not see this bath. On the other hand, the strong band-edge divergence of the particle-hole density of states leads to an undamped polaritonlike mode of the dressed phonons above the band edge of the particle-hole excitations. These undamped modes contribute to the lack of thermalization of long wavelength phonons at high temperatures. In higher dimensions, these constraints and the divergence of density of states are weakened and lead to thermalization at all wavelengths.

DOI: 10.1103/physrevb.106.024306

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