Microscopic Theory of Superconducting Phase Diagram in Infinite-Layer Nickelates

TL;DR

This paper develops a microscopic theory explaining the superconducting phase diagram of infinite-layer nickelates, highlighting the roles of Mottness and Hundness, and reproducing experimental observations of the superconducting dome.

Contribution

It introduces a fundamental model-based approach revealing the orbital-dependent strong correlations and the origin of the superconducting phase in nickelates, distinct from cuprates and iron pnictides.

Findings

Weak insulator phases are driven by Mottness and Hundness.

Superconductivity emerges in the transition regime between Mott and Hund insulators.

The theory reproduces the experimentally observed superconducting dome.

Abstract

Since the discovery of superconductivity in infinite-layer nickelates RNiO$_2$ (R=La, Pr, Nd), great research efforts have been paid to unveil its underlying superconducting mechanism. However, the physical origin of the intriguing hole-doped superconductivity phase diagram, characterized by a superconductivity dome sandwiched between two weak insulators, is still unclear. Here, we present a microscopic theory for electronic structure of nickelates from a fundamental model-based perspective. We found that the appearance of weak insulator phase in lightly and heavily hole-doped regime is dominated by Mottness and Hundness, respectively, exhibiting a unique orbital-selective doping originated from the competition of Hund interaction and crystal field splitting. Moreover, the superconducting phase can also be created in the "mixed" transition regime between Mott-insulator and Hund-induced insulator, exactly reproducing the experimentally observed superconducting phase diagram. Our findings not only demonstrate the orbital-dependent strong-correlation physics in Ni 3$d$ states, but also provide a unified understanding of superconducting phase diagram in hole-doped infinite-layer nickelates, which are distinct from the well-established paradigms in cuprates and iron pnictides.