Optical conductivity of polaronic charge carriers

TL;DR

This paper investigates the optical conductivity of charge carriers coupled to phonons in a one-dimensional model, revealing deviations from simple theories at intermediate coupling and finite density, with results aligning well with experimental observations.

Contribution

It provides exact and analytical results for polaronic optical conductivity in the Holstein model, especially at finite densities, highlighting deviations from traditional weak-coupling theories.

Findings

Analytical results agree well with exact data.

Characteristic polaronic excitations match experimental observations.

Deviations from weak-coupling and small-polaron theories are identified.

Abstract

The optical conductivity of charge carriers coupled to quantum phonons is studied in the framework of the one-dimensional spinless Holstein model. For one electron, variational diagonalisation yields exact results in the thermodynamic limit, whereas at finite carrier density analytical approximations based on previous work on single-particle spectral functions are obtained. Particular emphasis is put on deviations from weak-coupling, small-polaron or one-electron theories occurring at intermediate coupling and/or finite carrier density. The analytical results are in surprisingly good agreement with exact data, and exhibit the characteristic polaronic excitations observed in experiments on manganites.