Department of Materials Science and Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA.
Department of Nano-Semiconductor and Engineering, Korea University, Seoul 02841, Korea.
Science. 2020 Dec 18;370(6523):1438-1442. doi: 10.1126/science.aba5555.
A tenet of special relativity is that no particle can exceed the speed of light. In certain magnetic materials, the maximum magnon group velocity serves as an analogous relativistic limit for the speed of magnetic solitons. Here, we drive domain walls to this limit in a low-dissipation magnetic insulator using pure spin currents from the spin Hall effect. We achieve record current-driven velocities in excess of 4300 meters per second-within ~10% of the relativistic limit-and we observe key signatures of relativistic motion associated with Lorentz contraction, which leads to velocity saturation. The experimental results are well explained through analytical and atomistic modeling. These observations provide critical insight into the fundamental limits of the dynamics of magnetic solitons and establish a readily accessible experimental framework to study relativistic solitonic physics.
狭义相对论的一个基本原理是，没有粒子能够超过光速。在某些磁性材料中，最大磁振子群速度充当了磁孤子速度的相对论极限。在这里，我们利用自旋霍尔效应中的纯自旋流，在低损耗磁性绝缘体中将畴壁驱动到这一极限。我们实现了超过 4300 米每秒的创纪录电流驱动速度-接近相对论极限的 10% - 并且我们观察到了与洛伦兹收缩相关的相对论运动的关键特征，这导致了速度饱和。实验结果通过分析和原子尺度建模得到了很好的解释。这些观察结果为磁孤子动力学的基本极限提供了重要的见解，并建立了一个易于访问的实验框架来研究相对论孤子物理。
