Dynamical Mean Field Studies of Infinite Layer Nickelates: Physics Results and Methodological Implications

Abstract

This article summarizes recent work on the many-body (beyond density functional theory) electronic structure of layered rare-earth nickelates, both in the context of the materials themselves and in comparison to the high-temperature superconducting (high-Tc) layered copper-oxide compounds. It aims to outline the current state of our understanding of layered nickelates and to show how the analysis of these fascinating materials can shed light on fundamental questions in modern electronic structure theory. A prime focus is determining how the interacting physics defined over a wide energy range can be estimated and “downfolded” into a low energy theory that would describe the relevant degrees of freedom on the ∼0.5 eV scale and that could be solved to determine superconducting and spin and charge density wave phase boundaries, temperature dependent resistivities, and dynamical susceptibilities.

Magnetic Properties and Pseudogap Formation in Infinite-Layer Nickelates: Insights From the Single-Band Hubbard Model

“…1 as a function of temperature T and doping δ by applying three numerical methods. Besides dynamical mean-field theory (DMFT) [31][32][33][34], which includes all temporal onsitecorrelations of the lattice problem, we use two complementary extensions of it: cellular dynamical mean-field theory (CDMFT) [35] and the dynamical vertex approximation (DΓA) [36,37], a diagrammatic extension of DMFT [38]. The combination of complementary numerical methods ("multi-method approach" [39,40]) turned out to be very useful and versatile recently for both purely model- [39,41] and material-based [18] studies.…”

Optical Properties of Superconducting Nd0.8Sr0.2NiO2 Nickelate

“…While for weakly correlated metals, such as gold and silver, one obtains ω p 2 /(ω p 2 + (ω p MIR ) 2 ) ∼ 1, for Nd 0.8 Sr 0.2 NiO 2 , this ratio reaches a value of about 0.32 ± 0.06 at 300 K. This value can be compared to those of other correlated oxides like V 2 O 3 (∼0.18) and cuprates (0.2–0.4), identifying Nd 0.8 Sr 0.2 NiO 2 as a strongly correlated electronic system. This is an important result of our paper as it provides an experimental constraint for all theoretical models describing the low-energy electronic states of NiO 2 …”

“…Indeed, the description of the electronic structure near the Fermi level might require up to three bands and their hybridization, and contributions coming from the 4 f shells have also been proposed . Furthermore, the role of electronic correlations has been pointed out recently, although an experimental estimate of their importance is still lacking. On the other hand, the electron–phonon coupling has been ruled out as the exclusive origin of the observed superconductivity, with spin fluctuations playing a key role despite the absence of long-range magnetic order. , …”

Why Calculate in Infinite Dimensions?

“…Surfaces, layers, and nanostructures DMFT studies of inhomogeneous systems greatly improved our understanding of correlation effects at surfaces and interfaces, in thin films and multi-layered nanostructures [150] and, most recently, in infinite layer nickelates [151]. Thereby they provided a new understanding of potential functionalities of such structures and their application in electronic devices.…”