Complexity in Strongly Correlated Electronic Systems

TL;DR

This paper reviews the complex electronic phenomena in strongly correlated materials, highlighting the emergence of nanoscale structures and competing phases that influence their physical properties and potential applications.

Contribution

It synthesizes recent experimental and theoretical insights into electronic complexity, emphasizing the role of multiple active degrees of freedom and phase competition in correlated systems.

Findings

Electronic inhomogeneity is common in transition metal oxides.

Competing phases lead to giant responses to small perturbations.

Nanoscale structures are crucial for understanding high-temperature superconductivity.

Abstract

A wide variety of experimental results and theoretical investigations in recent years have convincingly demonstrated that several transition metal oxides and other materials, have dominant states that are not spatially homogeneous. This occurs in cases in which several physical interactions -- spin, charge, lattice, and/or orbital -- are simultaneously active. This phenomenon causes interesting effects, such as colossal magnetoresistance, and it also appears crucial to understand the high temperature superconductors. The spontaneous emergence of electronic nanometer-scale structures in transition metal oxides, and the existence of many competing states, are properties often associated with complex matter where nonlinearities dominate, such as soft materials and biological systems. This electronic complexity could have potential consequences for applications of correlated electronic materials, because not only charge (semiconducting electronic), or charge and spin (spintronics) are of relevance, but in addition the lattice and orbital degrees of freedom are active, leading to giant responses to small perturbations. Moreover, several metallic and insulating phases compete, increasing the potential for novel behavior.