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Modern Physics Letters B

Ground State Properties of Three-Dimensional Acoustic Polarons

Xiaoqun Wang

Published Aug 20, 1998• 6 citations
Publisher

Abstract

The ground state properties of a three-dimensional acoustic polaron are studied using the path integral Monte Carlo technique. In the strong coupling regime, there exists a self-trapped state, which originates from a short ranged electron–phonon interaction, and is of delocalized nature.
DOI
10.1142/s0217984998000901

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We study the structure of the ground-state wave function for a general model of a continuum polaron in d dimensions, coupled to either optical or acoustical phonons. Using a path-integral approach we derive a simple criterion which is sufficient to guarantee that the exact ground state is delocalized. This criterion applies to most polaron models studied so far and thus implies that interaction with phonons generally does not lead to a breaking of the translational symmetry, even for arbitrary strong coupling. We discuss briefly the distinction between self-trapping and localization.
We present a 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. This study shows that the acoustic lattice polaron represents a distinct quantum object with unique features, markedly different from any previously considered polaron model. In particular, the acoustic lattice polaron exhibits an interplay between long- and short wavelength acoustic vibrations, resulting in a composite phonon cloud which leads to the formation of multiple competing polaron states with a complex spectral response.
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