Slater to Mott crossover in the metal to insulator transition of Nd2Ir2O7

TL;DR

This study investigates the electronic structure of Nd2Ir2O7 across its magnetic metal-insulator transition, revealing a crossover from Slater to Mott insulating behavior and explaining the absence of Weyl points.

Contribution

It provides direct experimental evidence of the Slater to Mott crossover in Nd2Ir2O7 using angle-resolved photoemission spectroscopy.

Findings

Metallic phase has a quadratic band touching at the Fermi level.

Gap opens below the transition temperature, resembling a band insulator.

At low temperatures, quasiparticle peaks vanish, indicating Mott insulating behavior.

Abstract

We present an angle-resolved photoemission study of the electronic structure of the three-dimensional pyrochlore iridate Nd2Ir2O7 through its magnetic metal-insulator transition. Our data reveal that metallic Nd2Ir2O7 has a quadratic band, touching the Fermi level at the Gamma point, similarly to that of Pr2Ir2O7. The Fermi node state is, therefore, a common feature of the metallic phase of the pyrochlore iridates. Upon cooling below the transition temperature, this compound exhibits a gap opening with an energy shift of quasiparticle peaks like a band gap insulator. The quasiparticle peaks are strongly suppressed, however, with further decrease of temperature, and eventually vanish at the lowest temperature, leaving a non-dispersive flat band lacking long-lived electrons. We thereby identify a remarkable crossover from Slater to Mott insulators with decreasing temperature. These observations explain the puzzling absence of Weyl points in this material, despite its proximity to the zero temperature metal-insulator transition.