Mott-Hubbard transition and spin-liquid state on the pyrochlore lattice

TL;DR

This study investigates the Mott-Hubbard transition on the pyrochlore lattice, revealing a progression from a non-magnetic metal to a spin-disordered metal and finally to a Mott insulator, highlighting the role of magnetic fluctuations.

Contribution

It introduces a static auxiliary-field Monte Carlo method to analyze magnetic fluctuations and the metal-insulator transition on the pyrochlore lattice at finite temperatures.

Findings

Identification of a spin disordered metallic phase with small local moments

Observation of a pseudogap window before the Mott insulator transition

Resistivity diverges at the critical interaction strength

Abstract

The pyrochlore lattice involves corner sharing tetrahedra and the resulting geometric frustration is believed to suppress any antiferromagnetic order for Mott insulators on this structure. There are nevertheless short-range correlations which could be vital near the Mott-Hubbard insulator-metal transition. We use a static auxiliary-field-based Monte Carlo to study this problem in real space on reasonably large lattices. The method reduces to unrestricted Hartree-Fock at zero temperature but captures the key magnetic fluctuations at finite temperature. Our results reveal that increasing interaction drives the non magnetic (semi) metal to a 'spin disordered' metal with small local moments, at some critical coupling, and then, through a small pseudogap window, to a large moment, gapped, Mott insulating phase at a larger oupling. The spin disordered metal has a finite residual resistivity which grows with interaction strength, diverging at the upper coupling. We present the resistivity, optical conductivity, and density of states across the metal-insulator transition and for varying temperature. These results set the stage for the more complex cases of Mott transition in the pyrochlore iridates and molybdates.