Precise Measurement of Optical Reflectivity Spectra Using Defect-Free Surface of La(1-x)Sr(x)MnO(3): Evidence Against Extremely Small Drude Weight

TL;DR

This study precisely measures the optical reflectivity spectra of La(1-x)Sr(x)MnO(3) surfaces, showing that previous reports of extremely small Drude weight were due to surface damage, and providing insights into the material's electronic structure.

Contribution

It provides accurate optical conductivity measurements of La(1-x)Sr(x)MnO(3) surfaces, clarifying the true Drude weight and its implications for electronic properties.

Findings

Large spectral weight below 1.6 eV in optical conductivity

Previous small Drude weight results were due to surface damage

Sr substitution influences electronic structure and optical spectra

Abstract

Optical reflectivity spectra of La(1-x)Sr(x)MnO(3) (0<=x<=0.30) were measured on cleavage surfaces of single crystals. The optical conductivity $\sigma(w) of ferromagnetic-metal La(0.70)Sr(0.30)MnO(3) is characterized by a Drude-like - but not simple Drude - component with large spectral weight below 1.6 eV, which yields a large effective carrier number N*_eff consistent with the results of Hall coefficient and specific heat measurements. The present result demonstrates that the previous result of "small Drude weight" originates from the damage of the sample surface. The Sr-substitution effect on the electronic structure and the origin of the unconventional $\sigma(w) are also discussed.