Efimov effect in quantum magnets

TL;DR

This paper demonstrates that the Efimov effect, known in few-body physics, can occur in quantum magnets with magnons, showing universal scaling and proposing experimental observation methods.

Contribution

It reveals the Efimov effect in quantum magnets using an anisotropic Heisenberg model, extending universality to condensed matter systems.

Findings

Identification of anisotropy-induced two-magnon resonances

Calculation of three-magnon binding energies fitting universal scaling

Proposals for experimental realization and observation of Efimov states

Abstract

Physics is said to be universal when it emerges regardless of the underlying microscopic details. A prominent example is the Efimov effect, which predicts the emergence of an infinite tower of three-body bound states obeying discrete scale invariance when the particles interact resonantly. Because of its universality and peculiarity, the Efimov effect has been the subject of extensive research in chemical, atomic, nuclear and particle physics for decades. Here we employ an anisotropic Heisenberg model to show that collective excitations in quantum magnets (magnons) also exhibit the Efimov effect. We locate anisotropy-induced two-magnon resonances, compute binding energies of three magnons and find that they fit into the universal scaling law. We propose several approaches to experimentally realize the Efimov effect in quantum magnets, where the emergent Efimov states of magnons can be observed with commonly used spectroscopic measurements. Our study thus opens up new avenues for universal few-body physics in condensed matter systems.