Nematicity, magnetism and superconductivity in FeSe

TL;DR

This paper reviews the complex relationship between nematicity, magnetism, and superconductivity in FeSe, highlighting how external tuning parameters influence its phase diagram and superconducting properties.

Contribution

It provides a comprehensive overview of experimental and theoretical insights into FeSe's phases, emphasizing the effects of pressure and chemical substitutions.

Findings

Superconducting transition temperature varies from 8 K to nearly 40 K under different conditions.

Nematic phase extends over a wide temperature range and interacts with magnetic and superconducting phases.

External tuning parameters significantly modify FeSe's phase diagram and superconducting properties.

Abstract

Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, $T_\mathrm{c}$, ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.