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.

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Logic Circuits Are 2D semiconductors ready for next‐generation IC application? In article number 2202472, Yufeng Xie, Lifeng Bian, Wenzhong Bao, and co‐workers present a wafer‐scale demonstration by circuit‐level fabrication on a 4‐inch MoS2 wafer. While pass‐transistor configuration is more like an expedient to build logic circuits based on n‐type MoS2, future development should add complementary p‐type 2D semiconductors to realize more complex ICs.

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