Super-Diffusion In Quantum Spin Chains

一杯水中的一滴墨水会随着时间的推移向外扩散，最终使整个水的颜色均匀。另一方面，台球板上的球会滚来滚去，与其他球碰撞并分散开来。自然界中质量、能量或其他性质的传递似乎主要以两种方式发生，分别称为扩散和弹道。它们构成了我们对自然世界和宇宙的直觉。然而，物理学家怀疑可能还有其他新型的输运违背了我们的常识。例如，某些物质中磁波动的传输既不是扩散的，也不是弹道的，而是中间的。这种非常规的传输被称为超扩散，预计会发生在一维量子磁性材料中。同样令人兴奋的是，这种非常规的输运可以在室温下发生，这与我们naïve的预期相反，量子系统的独特行为应该只在极低的温度下观察到。这可能是一个有用的方面，潜在的应用，如在电子电气。在这个研究项目中，我的目标是提供量子磁体超扩散的第一个明确的实验证据。更具体地说，我将研究磁性离子主要沿着一个方向而不是三个方向耦合的晶体。这使得晶体本质上表现为一维磁性离子链的集合。我将使用核磁共振（NMR）技术，类似于核磁共振成像（MRI），来证明在这种一维量子链中，磁波动的传输以超扩散的方式发生。通过这项研究，我们将能够更好地了解量子材料的特性，这将为量子传感器或计算机等新量子技术的发展奠定基础。

A drop of ink in a glass of water will diffuse outwards with time, eventually colouring the whole of the water homogeneously. A ball on a billiard board, on the other hand, will roll around, colliding and scattering off other balls. Transport of mass, energy or other properties in nature seem to occur predominantly in either way, called diffusive and ballistic, respectively. They constitute our intuition into the natural world and universe. However, physicists suspect that there could be other new types of transport defying our common sense. For instance, the transport of magnetic fluctuations in certain materials could occur neither diffusively nor ballistically, but somewhat intermediate. This unconventional transport is called the super-diffusion and is predicted to occur in one-dimensional quantum magnetic materials. It is also exciting that such unconventional transport could occur at room temperature in contrast with our naïve expectation that unique behaviour from quantum systems should be only observed at extremely low temperature. This could be a useful aspect for potential application such as in Spnitronics. In this research project, I aim to provide the first clear experimental evidence for super-diffusion in quantum magnets. More specifically, I will look into crystals where magnetic ions are predominantly coupled along one direction, rather than three directions. This allows the crystals essentially behave as a collection of one-dimensional chain of magnetic ions. I will use Nuclear Magnetic Resonance (NMR) technique, akin to MRI, to evidence that the transport of magnetic fluctuations in such one-dimensional quantum chain occurs as super-diffusion. Through this research, we will be able to better understand the properties of quantum materials, which will underpin the development of new quantum technologies such as quantum sensors or computers.