Weyl Rings and enhanced susceptibilities in Pyrochlore Iridates: $k\cdot p$ Analysis of Cluster Dynamical Mean-Field Theory Results

TL;DR

This paper combines analytical and numerical methods to explore the topological and electronic properties of pyrochlore iridates, focusing on Weyl phases, their transitions, and related susceptibilities.

Contribution

It provides a detailed analysis of Weyl rings and phase transitions in pyrochlore iridates using $k ext{-}p$ theory and cluster DMFT results, highlighting small energy scales and flat bands.

Findings

Identification of Weyl rings and their properties

Enhanced susceptibilities due to flat Weyl bands

Frequency-dependent optical conductivities revealing energy scales

Abstract

We match analytic results to numerical calculations to provide a detailed picture of the metal-insulator and topological transitions found in density functional plus cluster dynamical mean-field calculations of pyrochlore iridates. We discuss the transition from Weyl metal to Weyl semimetal regimes, and then analyse in detail the properties of the Weyl semimetal phase and its evolution into the topologically trivial insulator. The energy scales in the Weyl semimetal phase are found to be very small, as are the anisotropy parameters. The electronic structure can to a good approximation be described as `Weyl rings' and one of the two branches that contributes to the Weyl bands is essentially flat, leading to enhanced susceptibilities. The optical longitudinal and Hall conductivities are determined; the frequency dependence includes pronounced features that reveal the basic energy scales of the Weyl semimetal phase.