Magnetic field-induced insulator-semimetal transition in a pyrochlore Nd2Ir2O7

TL;DR

This study explores how magnetic fields induce an insulator to semimetal transition in Nd2Ir2O7, revealing controllable topological states linked to magnetic order and electron correlation.

Contribution

It demonstrates magnetic field control over electronic phases and proposes a theoretical framework for exotic topological states in pyrochlore iridates.

Findings

Magnetic field along [111] controls metallic conduction at domain walls.

Field along [001] induces bulk insulator-semimetal transition.

Theoretical model predicts tunable topological states.

Abstract

We have investigated magneto-transport properties in a single crystal of pyrochore-type Nd2Ir2O7. The metallic conduction is observed on the antiferromagnetic domain walls of the all-in all-out type Ir-5d moment ordered insulating bulk state, that can be finely controlled by external magnetic field along [111]. On the other hand, an applied field along [001] induces the bulk phase transition from insulator to semimetal as a consequence of the field-induced modification of Nd-4f and Ir-5d moment configurations. A theoretical calculation consistently describing the experimentally observed features suggests a variety of exotic topological states as functions of electron correlation and Ir-5d moment orders which can be finely tuned by choice of rare-earth ion and by magnetic field, respectively.