RKKY interactions and anomalous Hall effect in metallic rare-earth pyrochlores

TL;DR

This paper investigates the RKKY interactions and anomalous Hall effect in metallic rare-earth pyrochlores, revealing a novel Weyl metallic phase with coexisting magnetic orders and broken symmetries, relevant to Pr2Ir2O7.

Contribution

It derives the RKKY interaction for non-Kramers doublets in pyrochlores and uncovers a new magnetic phase with topological and transport properties.

Findings

Discovery of a Weyl metallic phase with anomalous Hall effect

Identification of a magnetic order breaking time-reversal symmetry

Reconstruction of electronic band structure due to magnetic ordering

Abstract

Motivated by experiments on Pr2Ir2O7, we consider metallic pyrochlore systems A2B2O7, where the A-sites are occupied by rare-earth local moments and the B-sites host 5d transition metal ions with itinerant strongly spin-orbit coupled electrons. Assuming non-Kramers doublets on the A-site, we derive the RKKY interaction between them mediated by the B-site itinerant electrons and find extended non-Heisenberg interactions. Analyzing a simplified model of the RKKY interaction, we uncover a local moment phase with coexisting spiral Ising-like magnetic dipolar and XY-like quadrupolar ordering. This state breaks time-reversal and lattice symmetries, and reconstructs the B-site electronic band structure, producing a Weyl Metallic phase with an intrinsic anomalous Hall effect and an undetectably small magnetization. We discuss implications of our results for Pr2Ir2O7.