A Scaling Behavior of Spectral Weight Changes in Perovskite Manganites La_{0.7-y}Pr_{y}Ca_{0.3}MnO_3

TL;DR

This study investigates the optical spectral weight changes in La_{0.7-y}Pr_{y}Ca_{0.3}MnO_3 manganites, revealing a universal scaling behavior linked to theoretical models involving spin and lattice interactions.

Contribution

It demonstrates a universal scaling law for spectral weight in manganites and connects experimental results with a theoretical model including spin and Jahn-Teller effects.

Findings

Spectral weight below 0.5 eV increases with decreasing temperature in metallic samples.

All measured N_{eff}(0.5 eV)/T_C values fall onto a single scaling curve.

Pr doping suppresses far-infrared conductivities, likely due to Anderson localization.

Abstract

Optical conductivity spectra of La_{0.7-y}Pr_{y}Ca_{0.3}MnO_3 were systematically investigated. For metallic samples, the spectral weight below 0.5 eV, whose magnitude can be represented by the effective carrier number N_{eff}(0.5 eV), increases as temperature becomes lower. Regardless of the Pr doping, all the measured values of N_{eff}(0.5 eV)/T_C fall into one scaling curve. This scaling behavior could be explained by the theoretical model by Roeder et al. [Phys. Rev. Lett. 76, 1356 (1996)], which includes spin double exchange and Jahn-Teller lattice coupling to holes. With the Pr doping, far-infrared conductivities were found to be suppressed, probably due to the Anderson localization.