Polaron features for long-range electron-phonon interaction

TL;DR

This paper extends a variational approach to study polaron features in systems with long-range electron-phonon interactions, revealing significant mixing of electronic and phononic states and proposing a phase diagram.

Contribution

It introduces an extended variational method for long-range interactions and compares results with the short-range Holstein model, highlighting new polaron behaviors.

Findings

Strong mixing of electronic and phononic degrees of freedom at small coupling

Differences between long-range and short-range polaron features

A proposed polaron phase diagram

Abstract

The polaron features for long-range electron-phonon interaction are investigated by extending a variational approach previously proposed for the study of systems with local coupling. The ground-state spectral weight, the average kinetic energy, the mean number of phonons, and the electron-lattice correlation function are discussed for a wide range of model parameters focusing on the adiabatic regime and comparing the results with the short-range case (Holstein model). A strong mixing of electronic and phononic degrees of freedom for small values of the electron-phonon coupling constant is found in the adiabatic case due to the long-range interaction. Finally a polaron "phase diagram" is proposed.