Optical spectroscopy study on single crystalline LaFeAsO

TL;DR

This study investigates the optical properties of single crystalline LaFeAsO, revealing electronic correlations, spectral weight suppression with temperature, and the nature of magnetic ordering, highlighting the itinerant character of Fe 3d electrons.

Contribution

It provides detailed optical spectroscopy data on LaFeAsO, emphasizing the itinerant nature of magnetic order and the coexistence of electronic correlations and spin interactions.

Findings

Spectral weight suppression near 0.6 eV with decreasing temperature

Observation of spin-density-wave gap formation in the broken-symmetry state

Long-range magnetic order has a predominantly itinerant origin

Abstract

Millimeter-sized single crystals of LaFeAsO were grown from NaAs flux and the in-plane optical properties were studied over a wide frequency range. A sizable electronic correlation effect was indicated from the analysis of the free-carrier spectral weight. With decreasing temperature from 300 K, we observed a continuous suppression of the spectral weight near 0.6 eV. But a spin-density-wave gap formation at lower energy scale was seen only in the broken-symmetry state. We elaborate that both the itinerancy and local spin interactions of Fe\emph{3d} electrons are present for the FeAs-based systems; however, the establishment of the long-range magnetic order at low temperature has a dominantly itinerant origin.