# Square Lattice Iridates

## TL;DR

This paper reviews the electronic properties of Sr$_2$IrO$_4$, highlighting its similarities to cuprates, discussing potential for high-temperature superconductivity, and exploring how spin-orbit coupling influences its low-energy physics.

## Contribution

It provides a comprehensive analysis of iridates' electronic structures and their relation to cuprates, emphasizing the role of spin-orbit coupling in high-temperature superconductor research.

## Key findings

- Iridates exhibit cuprate-like phenomena such as pseudogaps and Fermi arcs.
- Strong spin-orbit coupling shapes the low-energy physics of Sr$_2$IrO$_4$.
- Potential pathways for high-temperature superconductivity in iridates are discussed.

## Abstract

Over the last few years, Sr$_2$IrO$_4$, a single-layer member of the Ruddlesden-Popper series iridates, has received much attention as a close analog of cuprate high-temperature superconductors. Although there is not yet firm evidence for superconductivity, a remarkable range of cuprate phenomenology has been reproduced in electron- and hole-doped iridates including pseudogaps, Fermi arcs, and $d$-wave gaps. Further, a number of symmetry breaking orders reminiscent of those decorating the cuprate phase diagram have been reported using various experimental probes. We discuss how the electronic structures of Sr$_2$IrO$_4$ through strong spin-orbit coupling leads to the low-energy physics that had long been unique to cuprates, what the similarities and differences between cuprates and iridates are, and how these advance the field of high-temperature superconductivity by isolating essential ingredients of superconductivity from a rich array of phenomena that surround it. Finally, we comment on the prospect of finding a new high-temperature superconductor based on the iridate series.