Quantum nanomagnets and nuclear spins: an overview

TL;DR

This review discusses the quantum physics of nanomagnets coupled to nuclear spins, focusing on spin tunneling phenomena, the need for advanced theoretical models, and recent experimental challenges to current understanding.

Contribution

It provides an accessible overview of the complex interplay between nanomagnet tunneling and nuclear spin environments, emphasizing the necessity of non-perturbative approaches.

Findings

Quantum tunneling of nanomagnet spins is significantly influenced by nuclear spin interactions.

Perturbative methods are inadequate; a combined dynamical treatment is required.

Recent experiments reveal gaps in current theoretical models.

Abstract

This mini-review presents a simple and accessible summary on the fascinating physics of quantum nanomagnets coupled to a nuclear spin bath. These chemically synthesized systems are an ideal test ground for the theories of decoherence in mesoscopic quantum degrees of freedom, when the coupling to the environment is local and not small. We shall focus here on the most striking quantum phenomenon that occurs in such nanomagnets, namely the tunneling of their giant spin through a high anisotropy barrier. It will be shown that perturbative treatments must be discarded, and replaced by a more sophisticated formalism where the dynamics of the nanomagnet and the nuclei that couple to it are treated together from the beginning. After a critical review of the theoretical predictions and their experimental verification, we continue with a set of experimental results that challenge our present understanding, and outline the importance of filling also this last gap in the theory.