Spin glasses: Experimental facts, theoretical concepts, and open questions

TLDR

Spin glasses exhibit characteristic properties such as frustration and broken ergodicity, and are modeled by the Edwards–Anderson framework using replica methods and mean‑field theory, with related phenomena seen in dielectric and orientational glasses. The review aims to synthesize recent theoretical advances and experimental findings on spin glasses, emphasizing a dynamic perspective of the transition. The authors discuss Monte‑Carlo simulations and various theoretical approaches—including site‑disorder models, phenomenological frozen‑phase theories, competing order phase diagrams, the Néel superparamagnetism model, and links to other disordered systems—to elucidate spin‑glass behavior.

Abstract

This review summarizes recent developments in the theory of spin glasses, as well as pertinent experimental data. The most characteristic properties of spin glass systems are described, and related phenomena in other glassy systems (dielectric and orientational glasses) are mentioned. The Edwards-Anderson model of spin glasses and its treatment within the replica method and mean-field theory are outlined, and concepts such as "frustration," "broken replica symmetry," "broken ergodicity," etc., are discussed. The dynamic approach to describing the spin glass transition is emphasized. Monte Carlo simulations of spin glasses and the insight gained by them are described. Other topics discussed include site-disorder models, phenomenological theories for the frozen phase and its excitations, phase diagrams in which spin glass order and ferromagnetism or antiferromagnetism compete, the Ne\'el model of superparamagnetism and related approaches, and possible connections between spin glasses and other topics in the theory of disordered condensed-matter systems.