Photo-induced phase transitions (PIPTs) provide an ultrafast, energy-efficient way for precisely manipulating the topological properties of transition-metal ditellurides and can be used to stabilize a topological phase in an otherwise semiconducting material. Using first-principles calculations, we demonstrate that the PIPT in monolayer MoTe₂ from the semiconducting 2H phase to the topological 1T′ phase can be triggered purely by electronic excitations that soften multiple lattice vibrational modes. These softenings, driven by a Peierls-like mechanism within the conduction bands, lead to structural symmetry breaking within sub-picosecond timescales, which is shorter than the timescale of a thermally driven phase transition. The transition is predicted to be triggered by photons with energies over 1.96 eV, with an associated excited carrier density of 3.4 × 10¹⁴ cm⁻², which enables a controllable phase transformation by varying the laser wavelength. Our results provide insight into the underlying physics of the phase transition in 2D transition-metal ditellurides and show an ultrafast phase-transition mechanism for manipulation of the topological properties of 2D systems.

光致相变（PIPT）提供了一种超快，节能的方法，可精确地控制过渡金属二碲化物的拓扑特性，并可用于稳定其他半导体材料中的拓扑相。使用第一性原理计算，我们证明了单层MoTe ₂中的PIPT从半导电的2H相到拓扑的1T'相可以完全通过电子激励来触发，该激励会软化多个晶格振动模式。这些软化是由导带内的类似Peierls的机理驱动的，导致在亚皮秒级的时间尺度内破坏了结构对称性，该对称性比热驱动的相变的时间尺度短。预计该跃迁由能量超过1.96 eV的光子触发，相关的激发载流子密度为3.4×10 ¹⁴  cm ^-2，通过改变激光波长可以实现可控的相变。我们的结果提供了对2D过渡金属二碲化物中相变的基本物理学的了解，并显示了用于控制2D系统拓扑特性的超快速相变机制。