希少なナノ磁石に回路を印刷することで、コンピューティングに新たな風を吹き込む(Printing circuits on rare nanomagnets puts a new spin on computing)

「スピングラス」を記述する理論モデルは、脳機能や株式市場のダイナミクスなど、他の複雑なシステムにも広く用いられている Theoretical models describing ‘spin glasses’ are broadly used in other complex systems, including brain function and stock-market dynamics

2022-03-24 ロスアラモス国立研究所（LANL）

＜関連情報＞

• https://discover.lanl.gov/news/0324-printing-circuits
• https://www.nature.com/articles/s41567-022-01538-7

ナノ磁性人工ホップフィールドネットワークにおける動的ガラス転移の直接観察 Direct observation of a dynamical glass transition in a nanomagnetic artificial Hopfield network

Michael Saccone,Francesco Caravelli,Kevin Hofhuis,Sergii Parchenko,Yorick A. Birkhölzer,Scott Dhuey,Armin Kleibert,Sebastiaan van Dijken,Cristiano Nisoli &Alan Farhan
Nature Physics Published: 17 March 2022  https://doi.org/10.1038/s41567-022-01538-7

Abstract

Spin glasses, generally defined as disordered systems with randomized competing interactions^1,2, are a widely investigated complex system. Theoretical models describing spin glasses are broadly used in other complex systems, such as those describing brain function^3,4, error-correcting codes⁵ or stock-market dynamics⁶. This wide interest in spin glasses provides strong motivation to generate an artificial spin glass within the framework of artificial spin ice systems^7,8,9. Here we present the experimental realization of an artificial spin glass consisting of dipolar coupled single-domain Ising-type nanomagnets arranged onto an interaction network that replicates the aspects of a Hopfield neural network¹⁰. Using cryogenic X-ray photoemission electron microscopy (XPEEM), we performed temperature-dependent imaging of thermally driven moment fluctuations within these networks and observed characteristic features of a two-dimensional Ising spin glass. Specifically, the temperature dependence of the spin glass correlation function follows a power-law trend predicted from theoretical models on two-dimensional spin glasses¹¹. Furthermore, we observe clear signatures of the hard-to-observe rugged spin glass free energy¹ in the form of sub-aging, out-of-equilibrium autocorrelations¹² and a transition from stable to unstable dynamics^1,13.