Optical conductivity of the Frohlich polaron

TL;DR

This paper provides comprehensive numerical results for the optical conductivity of the three-dimensional Frohlich polaron across all coupling regimes, using a systematic-error free quantum Monte Carlo method and analytic continuation techniques.

Contribution

It introduces an accurate, systematic-error free computational approach for calculating optical conductivity of the Frohlich polaron in all coupling regimes, including strong coupling.

Findings

Optical conductivity spectra show broad peaks with a shoulder, lacking sharp resonances in strong coupling.

The results agree with some perturbative and non-perturbative approaches, clarifying the nature of excited states.

Large broadening of excited states explains the absence of sharp resonances in the spectrum.

Abstract

We present accurate results for optical conductivity of the three dimensional Frohlich polaron in all coupling regimes. The systematic-error free diagrammatic quantum Monte Carlo method is employed where the Feynman graphs for the momentum-momentum correlation function in imaginary time are summed up. The real-frequency optical conductivity is obtained by the analytic continuation with stochastic optimization. We compare numerical data with available perturbative and non-perturbative approaches to the optical conductivity and show that the picture of sharp resonances due to relaxed excited states in the strong coupling regime is ``washed out''by large broadening of these states. As a result, the spectrum contains only a single-maximum broad peak with peculiar shape and a shoulder.