Bose-Einstein condensation in quantum magnets

TLDR

Quantum magnets, whose dimensionality, lattice geometry, disorder, and particle concentration can be tuned by magnetic field, serve as versatile interacting boson systems that have revealed surprising behaviors over the past two decades. This review surveys experimental and theoretical studies of Bose‑Einstein condensation in quantum magnets, highlighting the diverse realizations and bosonic phases accessible in these systems. The authors synthesize experimental observations and theoretical models to characterize Bose‑Einstein condensation and related bosonic phases in quantum magnets. The review shows that controlled theoretical approaches have revealed unusual effects driven by frustration, dimensionality, or disorder.

Abstract

This article reviews experimental and theoretical work on Bose-Einstein condensation in quantum magnets. These magnets are natural realizations of gases of interacting bosons whose relevant parameters such as dimensionality, lattice geometry, amount of disorder, nature of the interactions, and particle concentration can vary widely between different compounds. The particle concentration can be easily tuned by applying an external magnetic field which plays the role of a chemical potential. This rich spectrum of realizations offers a unique possibility for studying the different physical behaviors that emerge in interacting Bose gases from the interplay between their relevant parameters. The plethora of other bosonic phases that can emerge in quantum magnets, of which the Bose-Einstein condensate is the most basic ground state, is reviewed. The compounds discussed in this review have been intensively studied in the last two decades and have led to important contributions in the area of quantum magnetism. In spite of their apparent simplicity, these systems often exhibit surprising behaviors. The possibility of using controlled theoretical approaches has triggered the discovery of unusual effects induced by frustration, dimensionality, or disorder.