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

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.

arXiv comment8 pages, 10 figures

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• Competing magnetic orders and multipolar Weyl fermions in 227 pyrochlore iridates
• Magnetotransport of single crystal Sm${}_2$Ir${}_2$O${}_7$ across the pressure-induced quantum-critical phase boundary
• Magnetic structures and electronic properties of cubic-pyrochlore ruthenates from first principles
• Fluorite-related iridate Pr${}_3$IrO${}_7$: Crystal growth, structure, magnetism, thermodynamic, and optical properties
• Metal-insulator transitions in pyrochlore oxides