Mott Quantum Critical Points at finite doping

TL;DR

This paper demonstrates that in strongly correlated materials, the Mott transition at finite doping evolves into a first-order transition between metals ending at a quantum critical point, linking Mott physics with critical phenomena.

Contribution

It introduces a theoretical framework showing how the Mott transition unfolds into a quantum critical point at finite doping, supported by a multi-orbital Hubbard model analysis.

Findings

Mott transition becomes a first-order transition between metals at finite doping.

A quantum critical point emerges at the end of the phase separation region.

The scenario applies broadly, including to iron-based and cuprate superconductors.

Abstract

Strongly correlated materials often undergo a Mott metal-insulator transition, which is tipically first-order, as a function of control parameters like pressure. Upon doping, rich phase diagrams with competing instabilities are found. Yet, the conceptual link between the interaction-driven Mott transition and the finite-doping behavior lacks a clear connection with the theory of critical phenomena. In a prototypical case of a first-order Mott transition the surface associated with the equation of state for the homogeneous system is "folded" so that in a range of parameters stable metallic and insulating phases exist and are connected by an unstable metallic branch. Here we show that tuning the chemical potential the zero-temperature equation of state gradually unfolds. Under general conditions, we find that the Mott transition evolves into a first-order transition between two metals, associated to a phase separation region ending in a quantum critical point (QCP) at finite doping. This scenario is here demonstrated solving a simple multi-orbital Hubbard model relevant for the Iron-based superconductors, but its origin - the splitting of the atomic ground state multiplet by a small energy scale, here Hund's coupling - is much more general. A strong analogy with cuprate superconductors is traced.