arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2207.07293cond-mat.dis-nncond-mat.stat-mechcond-mat.str-el
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有限温度下量子力学驱动的二维结构自旋玻璃

Quantum mechanically driven structural-spin glass in two dimensions at finite temperature

Chisa Hotta, Kazumasa Ueda, Masatoshi Imada

摘要:

在磁性材料中,自旋有时会冻结成空间无序的玻璃态。玻璃形成液体或结构玻璃经常以三维形式存在。然而,在二维(2D)中,据信自旋玻璃和结构玻璃两者在有限温度下永远不可能存在,因为它们被热波动破坏。利用大规模量子蒙特卡罗模拟,我们发现了一个量子力学驱动的二维玻璃相在有限的温度。我们的平台是一个在挫挫三角晶格上具有量子横场的伊辛自旋模型。通过以下三个步骤来理解本发明的玻璃相是如何形成的。首先,通过几何阻挫和量子涨落的相互作用,部分自旋自发形成反铁磁蜂窝状自旋超结构。然后,键相互作用中的小随机性作为对该超结构的相关扰动而起作用,并将其分解成{ \it域},使其成为结构玻璃。上层结构的玻璃质反过来又产生了一个随机的磁场,作用于剩余的波动自旋,并将它们冻结。由此形成的域的形状敏感地取决于淬火过程,这是玻璃的特征之一,源自多谷自由能景观。本系统仅由{ \it a single}自旋玻璃自由度组成,其自然不会单独成为结构玻璃,也不会单独成为自旋玻璃。然而,具有这两种性质的玻璃以共存的双组分玻璃、代数结构玻璃和长程有序自旋玻璃的形式出现。这种玻璃形成机制的新概念开辟了一条即使在低维系统中也能实现功能玻璃的途径。

英文摘要:

In magnetic materials, spins sometimes freeze into spatially disordered glassy states. Glass forming liquids or structural glasses are found very often in three dimensions. However, in two dimensions(2D) it is believed that both spin glass and structural glass can never exist at a finite temperature because they are destroyed by thermal fluctuations. Using a large-scale quantum Monte Carlo simulation, we discover a quantum-mechanically driven 2D glass phase at finite temperatures. Our platform is an Ising spin model with a quantum transverse field on a frustrated triangular lattice. How the present glass phase is formed is understood by the following three steps. First, by the interplay of geometrical frustration and quantum fluctuation, part of the spins spontaneously form an antiferromagnetic honeycomb spin-superstructure. Then, small randomness in the bond interaction works as a relevant perturbation to this superstructure and breaks it up into {\it domains}, making it a structural glass. The glassiness of the superstructure, in turn, generates an emergent random magnetic field acting on the remaining fluctuating spins and freezes them. The shape of domains thus formed depends sensitively on the quenching process, which is one of the characteristic features of glass, originating from a multi-valley free-energy landscape. The present system consists only of {\it a single} bistable Ising degree of freedom, which naturally does not become a structural glass alone nor a spin glass alone. Nevertheless, a glass having both types of nature emerges in the form of coexisting two-component glasses, algebraic structural-glass and long-range ordered spin-glass. This new concept of glass-forming mechanism opens a way to realize functional glasses even in low dimensional systems.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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