Mott Quantum Critical Points at finite doping

• Published in: arXiv.org 2022-03
• Main Authors: Chatzieleftheriou, Maria, Kowalski, Alexander, Berović, Maja, Amaricci, Adriano, Capone, Massimo, Lorenzo De Leo, Sangiovanni, Giorgio, Luca de' Medici
• Format: Article
• Language: English
• Subjects: Chemical potential; Critical phenomena; Critical point; Doping; Equations of state; Insulators; Metal-insulator transition; Parameters; Phase diagrams; Phase separation; Superconductors
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2203.02451

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.