标题： 太赫兹场对表面拓扑结构的探测，具有亚原子分辨率 显示英文标题

标题： Terahertz control of surface topology probed with subatomic resolution

摘要： 光致相变提供了一种动态调制体复杂材料中拓扑状态的方法。 然而，下一代器件需要具有接近量子极限的接触电阻和对局部电子性质的精确控制的纳米级结构。 层状材料WTe$_2$被认为是一种可能的外尔半金属，其拓扑保护的线性电子能带交叉处承载着无质量的手征费米子。 在此，我们展示了一种由体材料WTe$_2$表面单原子层的光致剪切运动所促成的拓扑相变，从而为纳米级器件概念打开了大门。 在原子尖端顶端增强的超快太赫兹场通过界面处的铁电偶极子与WTe$_2$的关键层间剪切模式共振耦合，诱导表面发生结构相变至亚稳态。 亚原子分辨率的差分成像结合混合层次密度泛函理论，揭示了顶层原子平面发生了7$\pm$3皮米的位移。 隧穿光谱将相变过程中的电子变化与能带结构中的电子和空穴口袋联系起来，表明顶层原子层中拓扑保护的费米弧表面态可被光致可逆湮灭。 显示英文摘要

摘要： Light-induced phase transitions offer a method to dynamically modulate topological states in bulk complex materials. Yet, next-generation devices demand nanoscale architectures with contact resistances near the quantum limit and precise control over local electronic properties. The layered material WTe$_2$ has gained attention as a likely Weyl semimetal, with topologically protected linear electronic band crossings hosting massless chiral fermions. Here, we demonstrate a topological phase transition facilitated by light-induced shear motion of a single atomic layer at the surface of bulk WTe$_2$, thereby opening the door to nanoscale device concepts. Ultrafast terahertz fields enhanced at the apex of an atomically sharp tip resonantly couple to the key interlayer shear mode of WTe$_2$ via a ferroelectric dipole at the interface, inducing a structural phase transition at the surface to a metastable state. Subatomically resolved differential imaging, combined with hybrid-level density functional theory, reveals a shift of 7 $\pm$ 3 picometres in the top atomic plane. Tunnelling spectroscopy links electronic changes across the phase transition with the electron and hole pockets in the band structure, suggesting a reversible, light-induced annihilation of the topologically-protected Fermi arc surface states in the top atomic layer.