Frustrated quantum rare-earth pyrochlores

TL;DR

This review explores the complex physics of frustrated quantum rare-earth pyrochlores, detailing their microscopic interactions, phases, and key material examples, while highlighting open questions and future research directions.

Contribution

It provides a comprehensive synthesis of current understanding of the microscopic physics, phases, and experimental/theoretical insights into quantum rare-earth pyrochlores, including future prospects.

Findings

Detailed analysis of exchange interactions and low-energy models

Summary of experimental and theoretical knowledge on key materials

Identification of open questions and future research directions

Abstract

In this review we provide an introduction to the physics of a series of frustrated quantum rare-earth pyrochlores. We first give a background on the microscopic single- and two-ion physics of these materials, discussing the origins and properties of their exchange interactions and their minimal low-energy effective models, before outlining what is known about their classical and quantum phases. We then make use of this understanding to discuss four important material examples: Er$_2$Ti$_2$O$_7$, Yb$_2$Ti$_2$O$_7$, Tb$_2$Ti$_2$O$_7$ and Pr$_2$Zr$_2$O$_7$, covering in some detail what is known experimentally and theoretically for each, and summarize some key questions that remain open. Finally, we offer an outlook on some alternative material platforms for realizing similar physics and discuss what we see as prospects for future investigations on these quantum rare-earth pyrochlores.