Carrier-density effects in many-polaron systems

TL;DR

This paper reviews theoretical insights into many-polaron systems at finite charge density, highlighting a crossover from polaronic to metallic behavior and analyzing spectral and correlation functions.

Contribution

It offers a unified review of numerical and analytical results on spectral properties of many-polaron systems, emphasizing the density-driven crossover and ruling out phase separation.

Findings

Crossover from polaronic to metallic state with increasing density

Phonon spectral function reveals density effects on quasiparticles

No evidence found for phase separation in the model

Abstract

Many-polaron systems with finite charge-carrier density are often encountered experimentally. However, until recently, no satisfactory theoretical description of these systems was available even in the framework of simple models such as the one-dimensional spinless Holstein model considered here. In this work, previous results obtained using numerical as well as analytical approaches are reviewed from a unified perspective, focussing on spectral properties which reveal the nature of the quasiparticles in the system. In the adiabatic regime and for intermediate electron-phonon coupling, a carrier-density driven crossover from a polaronic to a rather metallic system takes place. Further insight into the effects due to changes in density is gained by calculating the phonon spectral function, and the fermion-fermion and fermion-lattice correlation functions. Finally, we provide strong evidence against the possibility of phase separation.