Direct observation of displaced phonons responsible for small polaron charge transport in (La1/3Sm2/3)0.67Ba0.33-xSrxMnO3 (x = 0.0, 0.1, 0.2 and 0.33)

TL;DR

This study directly observes displaced phonons in substituted manganites, revealing their role in small polaron charge transport and how electron-phonon coupling strength influences phonon modes and charge mobility.

Contribution

It provides direct IR-spectra evidence of displaced phonons associated with small polaron transport in manganites, highlighting the impact of electron-phonon coupling.

Findings

Displaced phonons appear in IR spectra with strong coupling.

Charge transport occurs via polarons formed through electron-phonon interactions.

Phonon modes change distinctly with coupling strength.

Abstract

It is shown that charge transport in substituted manganites (La1/3Sm2/3)0.67Ba0.33-xSrxMnO3 (x = 0.0, 0.1, 0.2 and 0.33) is through polarons which are formed through electron-phonon coupling whose strength determines the mobility of the charge carrier. For weak coupling the free phonon mode is only slightly affected but in strong coupling the free phonon mode disappears and "displaced" phonon modes appear. This is seen directly in IR-spectra.