Diagrammatic Monte Carlo study of the Fr\"ohlich polaron dispersion in 2D and 3D

TL;DR

This study uses Diagrammatic Monte Carlo to accurately compute polaron energies, masses, and dispersion in 2D and 3D, confirming theoretical scaling laws and providing benchmarks across coupling regimes.

Contribution

It applies and validates the DMC method for Fröhlich polarons in 2D and 3D, confirming analytical scaling and expanding the understanding of polaron properties.

Findings

DMC results match Feynman formalism benchmarks.

Verified 3D to 2D scaling relations for energies and masses.

Computed dispersion curves consistent with analytical limits.

Abstract

We present results for the solution of the large polaron Fr\"ohlich Hamiltonian in 3-dimensions (3D) and 2-dimensions (2D) obtained via the Diagrammatic Monte Carlo (DMC) method. Our implementation is based on the approach by Mishchenko [A.S. Mishchenko et al., Phys. Rev. B 62, 6317 (2000)]. Polaron ground state energies and effective polaron masses are successfully benchmarked with data obtained using Feynman's path integral formalism. By comparing 3D and 2D data, we verify the analytically exact scaling relations for energies and effective masses from 3D$\to$2D, which provides a stringent test for the quality of DMC predictions. The accuracy of our results is further proven by providing values for the exactly known coefficients in weak- and strong coupling expansions. Moreover, we compute polaron dispersion curves which are validated with analytically known lower and upper limits in the small coupling regime and verify the first order expansion results for larger couplings, thus disproving previous critiques on the apparent incompatibility of DMC with analytical results and furnishing useful reference for a wide range of coupling strengths.