Departimento di Fisica, Universitá di Roma La Sapienza, Istituto Nazionale di Fisica Nucleare, Sezione di Roma I, I-00185 Rome, Italy.
Proc Natl Acad Sci U S A. 2013 Feb 19;110(8):2752-7. doi: 10.1073/pnas.1222848110. Epub 2013 Feb 4.
Glass transition, in which viscosity of liquids increases dramatically upon decrease of temperature without any major change in structural properties, remains one of the most challenging problems in condensed matter physics despite tremendous research efforts in past decades. On the other hand, disordered freezing of spins in magnetic materials with decreasing temperature, the so-called "spin glass transition," is understood relatively better. A previously found similarity between some spin glass models and the structural glasses inspired development of theories of structural glasses based on the scenario of spin glass transition. This scenario, although it looks very appealing, is still far from being well established. One of the main differences between standard spin systems and molecular systems is the absence of quenched disorder and the presence of translational invariance: it often is assumed that this difference is not relevant, but this conjecture still needs to be established. The quantities, which are well-defined and characterized for spin models, are not easily calculable for molecular glasses because of the lack of quenched disorder that breaks the translational invariance in the system. Thus the characterization of the similarity between spin and the structural glass transition remains an elusive subject. In this study, we introduced a model structural glass with built-in quenched disorder that alleviates this main difference between the spin and molecular glasses, thereby helping us compare these two systems: the possibility of producing a good thermalization at rather low temperatures is one of the advantages of this model.
玻璃化转变是凝聚态物理中最具挑战性的问题之一,尽管在过去几十年中进行了大量的研究,但它仍然存在。在另一方面,随着温度的降低,磁性材料中自旋的无序冻结,即所谓的“自旋玻璃转变”,相对来说理解得更好。先前在一些自旋玻璃模型和结构玻璃之间发现的相似性激发了基于自旋玻璃转变情景的结构玻璃理论的发展。尽管这个情景看起来非常有吸引力,但它仍然远未得到很好的确立。标准自旋系统和分子系统之间的主要区别之一是缺少淬火无序和存在平移不变性:通常假设这种差异不重要,但这一假设仍需要得到证实。对于自旋模型,有一些定义明确且特征明显的量,但对于分子玻璃来说,由于缺乏破坏系统平移不变性的淬火无序,这些量不容易计算。因此,自旋和结构玻璃转变之间的相似性的特征仍然是一个难以捉摸的课题。在这项研究中,我们引入了一个带有内置淬火无序的模型结构玻璃,从而缓解了自旋和分子玻璃之间的主要区别,帮助我们比较这两个系统:在相当低的温度下产生良好热化的可能性是这个模型的一个优势。