Polar metals: Principles and Prospects

TL;DR

This review discusses the principles, recent progress, and future prospects of polar metals, materials that uniquely combine polarity and metallicity, with implications across multiple advanced electronic and quantum phenomena.

Contribution

It provides a comprehensive overview of the mechanisms, experimental realizations, and potential applications of polar metals, highlighting recent breakthroughs and future research directions.

Findings

First experimental examples: LiOsO3 and WTe2

Mechanisms for combining polarity and metallicity identified

Implications for topology, ferroelectricity, and spintronics

Abstract

We review the class of materials known as polar metals, in which polarity and metallicity coexist in the same phase. While the notion of polar metals was first invoked more than 50 years ago, their practical realization has proved challenging, since the itinerant carriers required for metallicity tend to screen any polarization. Huge progress has been made in the last decade, with many mechanisms for combining polarity and metallicity proposed, and the first examples, LiOsO3 and WTe2, identified experimentally. The availability of polar metallic samples has opened a new paradigm in polar metal research, with implications in the fields of topology, ferroelectricity, magnetoelectricity, spintronics, and superconductivity. Here, we review the principles and techniques that have been developed to design and engineer polar metals and describe some of their interesting properties, with a focus on the most promising directions for future work.