Exotic phenomena can be achieved in quantum materials by confining electronic states into two dimensions. For example, relativistic fermions are realized in a single layer of carbon atoms¹, the quantized Hall effect can result from two-dimensional (2D) systems^2,3, and the superconducting transition temperature can be considerably increased in a one-atomic-layer material^4,5. Ordinarily, a 2D electronic system can be obtained by exfoliating the layered materials, growing monolayer materials on substrates, or establishing interfaces between different materials. Here we use femtosecond infrared laser pulses to invert the periodic lattice distortion sectionally in a three-dimensional (3D) charge density wave material (1T-TiSe₂), creating macroscopic domain walls of transient 2D ordered electronic states with unusual properties. The corresponding ultrafast electronic and lattice dynamics are captured by time-resolved and angle-resolved photoemission spectroscopy⁶ and ultrafast electron diffraction at energies of the order of megaelectronvolts⁷. Moreover, in the photoinduced 2D domain wall near the surface we identify a phase with enhanced density of states and signatures of potential opening of an energy gap near the Fermi energy. Such optical modulation of atomic motion is an alternative path towards realizing 2D electronic states and will be a useful platform upon which novel phases in quantum materials may be discovered.

通过将电子态限制在二维中，可以在量子材料中实现奇异现象。例如，相对论费米子是在单层碳原子¹中实现的，二维 (2D) 系统可产生量子化霍尔效应^2,3，而单原子层中的超导转变温度可显着提高材料^4,5。通常，二维电子系统可以通过剥离层状材料、在基板上生长单层材料或在不同材料之间建立界面来获得。在这里，我们使用飞秒红外激光脉冲在三维 (3D) 电荷密度波材料 (1T-TiSe ₂), 创建具有异常特性的瞬态 2D 有序电子态的宏观畴壁。相应的超快电子和晶格动力学由时间分辨和角分辨光电子能谱⁶以及兆电子伏量级能量的超快电子衍射⁷捕获。此外，在表面附近的光致二维畴壁中，我们确定了一个状态密度增强的相和费米能量附近能隙潜在开放的特征。这种原子运动的光学调制是实现二维电子态的另一种途径，并将成为一个有用的平台，可以在该平台上发现量子材料的新相。