Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), 50009 Zaragoza, Spain.
Proc Natl Acad Sci U S A. 2012 Apr 24;109(17):6452-6. doi: 10.1073/pnas.1203295109. Epub 2012 Apr 9.
Spin glasses are a longstanding model for the sluggish dynamics that appear at the glass transition. However, spin glasses differ from structural glasses in a crucial feature: they enjoy a time reversal symmetry. This symmetry can be broken by applying an external magnetic field, but embarrassingly little is known about the critical behavior of a spin glass in a field. In this context, the space dimension is crucial. Simulations are easier to interpret in a large number of dimensions, but one must work below the upper critical dimension (i.e., in d < 6) in order for results to have relevance for experiments. Here we show conclusive evidence for the presence of a phase transition in a four-dimensional spin glass in a field. Two ingredients were crucial for this achievement: massive numerical simulations were carried out on the Janus special-purpose computer, and a new and powerful finite-size scaling method.
自旋玻璃是一种长期存在的模型，用于描述玻璃转变时出现的缓慢动力学。然而，自旋玻璃与结构玻璃在一个关键特征上有所不同：它们具有时间反演对称性。通过施加外磁场可以打破这种对称性，但令人尴尬的是，对于磁场中的自旋玻璃的临界行为知之甚少。在这种情况下，空间维度至关重要。在大量维度中，模拟更容易解释，但为了使结果与实验相关，必须在超临界维度（即 d<6）以下工作。在这里，我们提供了确凿的证据，证明磁场中存在一个四维度自旋玻璃的相变。实现这一目标的两个关键因素是：在 Janus 专用计算机上进行了大规模的数值模拟，以及一种新的强大的有限尺寸标度方法。
