Evolution of possible Weyl semimetal states across the hole-doping induced Mott transition in pyrochlore iridates

TL;DR

This study explores how hole-doping induces Weyl semimetal states in pyrochlore iridates, revealing diverse topological phases and unconventional transport phenomena linked to magnetic exchange interactions.

Contribution

It demonstrates the emergence of various Weyl semimetal states across the Mott transition in pyrochlore iridates, highlighting the role of f-d exchange interactions in stabilizing topological phases.

Findings

Observation of double Weyl and line-node semimetals in doped pyrochlore iridates.

Enhanced Hall angle near the Mott transition in Gd-based compounds.

Detection of unconventional Hall contributions linked to Weyl points.

Abstract

We study possible Weyl semimetals of strongly-correlated electrons by investigating magnetotransport properties in pyrochlore R2Ir2O7 (R=rare-earth ions), choosing three types of R ions to design the exchange coupling scheme between R 4f and Ir 5d moments; non-magnetic Eu (4f6), isotropic Gd (4f7), and anisotropic Tb (4f8). In the doping-induced semimetallic state, distinctive features of magnetoresistance and Hall effect are observed in R=Gd and Tb compounds due to the effects of the exchange-enhanced isotropic and anisotropic Zeeman fields, respectively, exemplifying the double Weyl semimetal and the 2-in 2-out line-node semimetal as predicted by theories. In particular, a Hall angle of R=Gd compound is strongly enhanced to 1.5 % near above the critical doping for the Mott transition. Furthermore, an unconventional Hall contribution is discerned for a lower doping regime of R=Gd compound, which can be ascribed to the emergence of Weyl points with the field-distorted all-in all-out order state. These findings indicate that the hole-doping induced Mott transition as well as the characteristic f-d exchange interaction stabilizes versatile topological semimetal states in a wide range of material parameter space.