Rare-earth spin textures and a route to electronic inhomogeneity in $Pr_2Ir_2O_7$

Abstract

The pyrochlore iridate $Pr_2Ir_2O_7$ remains metallic at low temperatures where its family members insulate. Recently, scanning tunneling spectroscopy experiments have revealed an inhomogeneous mixture of Kondo-screened and Kondo-destroyed regions when its surface is produced by cleaving at room temperature while it remains uniform when cleaved at low temperatures. We ask whether the frustrated praseodymium spin texture seeds this inhomogeneity. To study this, we produce Monte-Carlo-sampled Pr spin-ice configurations, presumed to evolve slowly in time, and couple through a local Kondo exchange $J_K$ to an eight-band Hartree-Fock model of the Ir electrons. We further find the charge gap of the all-in-all-out state common in the other family members closes smoothly with the coupling $J_K$, and the recently proposed monopole-rich ``jellyfish'' textures further suppress the insulating behavior by $ΔJ_{Kc}\approx 0.03\,t$. Additionally, scanning a small cluster across a large Pr surface yields a synthetic tunneling map that fractures into islands within a sea. Although our classical simulable theory omits the Kondo singlet, the spatial modulation of the Fermi-level density of states it produces is, through the exponential Doniach sensitivity of the Kondo temperature, sufficient to tip the local balance between screening and magnetic order; a frustration-driven route to the observed Kondo/Kondo-destroyed inhomogeneity.