Metal-Insulator and Superconductor-Insulator Transitions in Correlated Electron Systems

TL;DR

This paper investigates quantum phase transitions in correlated electron systems, focusing on the Mott insulator-metal transition, flat dispersion formation, and potential superconducting instabilities, highlighting critical behaviors and orbital effects.

Contribution

It introduces a detailed analysis of the dynamical exponent and flat dispersion effects near the Mott transition, including orbital degeneracy considerations.

Findings

Large dynamical exponent z=4 near transition

Formation of flat dispersion due to singular momentum dependence

Orbital correlation length diverges at the transition

Abstract

Quantum transitions between the Mott insulator and metals by controlling filling in two-dimensional square lattice are characterized by a large dynamical exponent $z=4$ where the origin of unusual metallic properties near the Mott insulator are ascribed to the proximity of the transition. The scaling near the transition indicates the formation of flat dispersion area due to singular momentum dependence of the single-particle renormalization. The flat dispersion controls critical properties of the Mott transition. An instability of the flat dispersion to the d-wave superconducting order is discussed. We also discuss a case of the Mott transition for a model of Mn perovskite compounds with orbital degeneracy where orbital correlation length shows critical divergence toward the metal-insulator transition.