Observation of fluctuation-mediated picosecond nucleation of a topological phase
Observation of fluctuation-mediated picosecond nucleation of a topological phase
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DOI：
10.1038/s41563-020-00807-1
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发表时间：
2020-10-05
期刊：
影响因子：
41.2
通讯作者：
Eisebitt, Stefan
中科院分区：
文献类型：
--
作者：
Buettner, Felix;Pfau, Bastian;Eisebitt, Stefan
利用时间分辨X射线散射证明了300ps的超快拓扑相变为天米子相。这种转变是通过形成一个暂态的拓扑涨落状态来实现的。物质的拓扑态显示出迷人的物理特性和内在的稳定性。一个关键的挑战是快速创建拓扑相，这需要大规模的电荷或自旋自由度的重新定向。在这里，我们报道了由许多磁天子组成的扩展拓扑相的皮秒出现。这一相的成核过程是通过红外激光激发后的单次软X射线散射实时进行的，其成核过程是由一个瞬时的拓扑涨落态来实现的。这种状态是通过时间反转对称破缺垂直磁场的存在而实现的，并且存在时间小于300ps。原子模拟表明，涨落态大大降低了拓扑能垒，从而使观察到的Skyrmion相快速而均匀地成核。这些观察结果提供了对拓扑相变本质的基本见解，并提出了一条通过中间涨落状态在各种材料中实现超快拓扑转换的途径。
Time-resolved X-ray scattering is utilized to demonstrate an ultrafast 300 ps topological phase transition to a skyrmionic phase. This transition is enabled by the formation of a transient topological fluctuation state.Topological states of matter exhibit fascinating physics combined with an intrinsic stability. A key challenge is the fast creation of topological phases, which requires massive reorientation of charge or spin degrees of freedom. Here we report the picosecond emergence of an extended topological phase that comprises many magnetic skyrmions. The nucleation of this phase, followed in real time via single-shot soft X-ray scattering after infrared laser excitation, is mediated by a transient topological fluctuation state. This state is enabled by the presence of a time-reversal symmetry-breaking perpendicular magnetic field and exists for less than 300 ps. Atomistic simulations indicate that the fluctuation state largely reduces the topological energy barrier and thereby enables the observed rapid and homogeneous nucleation of the skyrmion phase. These observations provide fundamental insights into the nature of topological phase transitions, and suggest a path towards ultrafast topological switching in a wide variety of materials through intermediate fluctuating states.