Magnetotransport and Phase competition in three-dimensional Hubbard-Holstein model at half-filling

TL;DR

This study explores the phase diagram and transport properties of the 3D Hubbard-Holstein model at half-filling, revealing multiple insulating and metallic phases, phase transitions, and pseudogap features through advanced simulations.

Contribution

It provides the first detailed phase diagram of the 3D Hubbard-Holstein model at half-filling, identifying multiple phases and transitions using exact diagonalization and Monte Carlo methods.

Findings

Identified two insulating phases: antiferromagnetic and charge-ordered.

Observed multiple phases including Mott-Hubbard and bipolaronic states.

Revealed strong proximity effects and pseudogap features near phase boundaries.

Abstract

We investigate the magnetotransport properties of the one-band Hubbard-Holstein model at half-filling in three dimensions (3D) using exact diagonalization based semi-classical Monte Carlo simulations with phonons treated in the adiabatic limit. The low-temperature electronic correlation $U$ vs electron-phonon coupling $V$ phase diagram reveals two insulating phases--antiferromagnetic (AF-I) and charge-ordered (CO-I)--separated by a first-order transition, with no metallic phase observed at their intersection, indicating robustness of these phases in 3D. For $U \sim bandwidth$, the $V$ vs temperature $T$ phase diagram exhibits multiple phases including AF-I, CO-I, Mott-Hubbard insulator, bipolaronic insulator, and two bipolaronic metallic states. Several first-order transitions occur near $V \sim 3.75$. Above the ordering temperature, the density of states shows universal behavior dominated by electronic contribution, while susceptibility and DOS analyses reveal pseudogap features. Magnetic and transport properties along the phase boundary highlight strong proximity effects between competing phases, suggesting routes for tuning correlated materials and emergent electronic states.