Single polaron properties of the breathing-mode Hamiltonian

TL;DR

This paper numerically studies the properties of 1D breathing-mode polarons, revealing a sharper large-to-small polaron crossover and non-monotonic dispersion at moderate to large couplings, contrasting with Holstein polarons.

Contribution

It introduces an extended variational scheme and Greens function computation for breathing-mode polarons, highlighting differences from Holstein polarons and uncovering new dispersion behaviors.

Findings

Sharper large-to-small polaron crossover observed

Non-monotonic dispersion at moderate and large couplings

Contrasts with previous self-consistent Born approximation results

Abstract

We investigate numerically various properties of the one-dimensional (1D) breathing-mode polaron. We use an extension of a variational scheme to compute the energies and wave-functions of the two lowest-energy eigenstates for any momentum, as well as a scheme to compute directly the polaron Greens function. We contrast these results with results for the 1D Holstein polaron. In particular, we find that the crossover from a large to a small polaron is significantly sharper. Unlike for the Holstein model, at moderate and large couplings the breathing-mode polaron dispersion has non-monotonic dependence on the polaron momentum k. Neither of these aspects is revealed by a previous study based on the self-consistent Born approximation.