Diagrammatic quantum Monte Carlo study of an acoustic lattice polaron

TL;DR

This study uses diagrammatic Monte Carlo methods to analyze an acoustic lattice polaron, revealing complex spectral features and self-trapping phenomena due to interplay of acoustic phonons, across different coupling regimes.

Contribution

First approximation-free diagrammatic Monte Carlo analysis of an acoustic lattice polaron with novel insights into self-trapping and spectral complexity.

Findings

Identification of a self-trapping region separating weak and strong coupling regimes.

Observation of quantum resonance between lattice deformations affecting ground state and spectral properties.

Discovery of complex spectral response due to interplay of long- and short-wavelength acoustic vibrations.

Abstract

We present the first approximation free diagrammatic Monte Carlo study of a lattice polaron interacting with an acoustic phonon branch through the deformation potential. Weak and strong coupling regimes are separated by a self-trapping region where quantum resonance between various possible lattice deformations is seen in the ground state properties, spectral function, and optical conductivity. The unique feature of such polaron is the interplay between long- and short wavelength acoustic vibrations creating a composite phonon cloud and leading to persistent self-trapping due to the existence of multiple quasi-stable states. This results in a spectral response whose structure is much more complex than in any of the previously considered polaron models.