Large and Small Polaron Excitations in La2/3(Sr/Ca)1/3MnO3 Films

TL;DR

This study investigates mid-infrared excitations in La2/3Sr1/3MnO3 and La2/3Ca1/3MnO3 thin films, identifying large polarons in one and small polarons in the other, revealing distinct polaronic behaviors across magnetic transitions.

Contribution

It provides a detailed analysis of MIR excitations in manganite films, distinguishing between large and small polaron models and establishing a scaling behavior in LSMO.

Findings

MIR resonance in LSMO attributed to large polarons

MIR resonance in LCMO attributed to small polarons

Scaling behavior observed in LSMO MIR resonance

Abstract

We present detailed optical measurements of the mid-infrared (MIR) excitations in thin films of La2/3Sr1/3MnO3 (LSMO) and La2/3Ca1/3MnO3 (LCMO) across the magnetic transition. The shape of the excitation at about 0.2 eV in both samples is analyzed in terms of polaron models. We propose to identify the MIR resonance in LSMO as the excitation of large polarons and that in LCMO as a small polaron excitation. A scaling behavior for the low-energy side of the polaronic MIR resonance in LSMO is established.