Department of Physics, University of California, Berkeley, CA, USA.
Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
Nature. 2021 Sep;597(7874):45-50. doi: 10.1038/s41586-021-03763-1. Epub 2021 Sep 1.
Conventional wisdom holds that macroscopic classical phenomena naturally emerge from microscopic quantum laws. However, despite this mantra, building direct connections between these two descriptions has remained an enduring scientific challenge. In particular, it is difficult to quantitatively predict the emergent 'classical' properties of a system (for example, diffusivity, viscosity and compressibility) from a generic microscopic quantum Hamiltonian. Here we introduce a hybrid solid-state spin platform, where the underlying disordered, dipolar quantum Hamiltonian gives rise to the emergence of unconventional spin diffusion at nanometre length scales. In particular, the combination of positional disorder and on-site random fields leads to diffusive dynamics that are Fickian yet non-Gaussian. Finally, by tuning the underlying parameters within the spin Hamiltonian via a combination of static and driven fields, we demonstrate direct control over the emergent spin diffusion coefficient. Our work enables the investigation of hydrodynamics in many-body quantum spin systems.
传统观点认为，宏观经典现象自然源自微观量子定律。然而，尽管有这种说法，但在这两种描述之间建立直接联系仍然是一个持久的科学挑战。特别是，从一般的微观量子哈密顿量中定量预测系统的新兴“经典”性质（例如扩散率、粘性和可压缩性）是很困难的。在这里，我们引入了一种混合固态自旋平台，其中基础的无序、偶极量子哈密顿量导致了非传统的自旋扩散在纳米尺度上的出现。特别是，位置无序和局域随机场的组合导致了扩散动力学是菲克型但非高斯型的。最后，通过组合静态和驱动场来调整自旋哈密顿量中的基本参数，我们证明了对新兴自旋扩散系数的直接控制。我们的工作使人们能够研究多体量子自旋系统中的流体动力学。
