Optical conductivity of the metallic pyrochlore iridate Pr$_2$Ir$_2$O$_7$: Influence of spin-orbit coupling and electronic correlations on the electronic structure

TL;DR

This study investigates the optical and electronic properties of Pr$_2$Ir$_2$O$_7$, revealing its metallic nature, correlation effects, and proximity to a Weyl semimetal phase influenced by spin-orbit coupling.

Contribution

It provides detailed experimental insights into the optical conductivity and electronic structure of Pr$_2$Ir$_2$O$_7$, highlighting the role of correlations and spin-orbit coupling in this pyrochlore iridate.

Findings

Pr$_2$Ir$_2$O$_7$ exhibits metallic behavior with no magnetic phase transitions down to 2 K.

Optical conductivity shows a temperature-dependent mid-infrared band indicating correlation effects.

The material is close to a Weyl semimetal phase, influenced by spin-orbit coupling.

Abstract

The synergy of strong spin-orbit coupling and electron-electron interactions gives rise to unconventional topological states, such as topological Mott insulator, Weyl semimetal, and quantum spin liquid. In this study, we have grown single crystals of the pyrochlore iridate Pr$_2$Ir$_2$O$_7$ and explored its magnetic, lattice dynamical, and electronic properties. While Raman spectroscopy data reveal six phonon modes confirming the cubic \textit{Fd$\bar{3}$m} crystal symmetry, dc magnetic susceptibility data show no anomalies and hence indicate the absence of magnetic phase transitions down to 2~K. Both temperature-dependent electric transport and optical conductivity data reveal the metallic character of Pr$_2$Ir$_2$O$_7$. The optical conductivity spectrum contains a mid-infrared absorption band, which becomes more pronounced with decreasing temperature due to spectral weight transfer from high to low energies. The presence of the mid-infrared band hints at the importance of correlation physics. The optical response furthermore suggests that Pr$_2$Ir$_2$O$_7$ is close to the Weyl semimetal phase.