Realization of fractional-layer transition metal dichalcogenides.

Zhao, Ya-Xin; Jin, Heng; Han, Zi-Yi; Zhao, Xinlei; Ren, Ya-Ning; Zhang, Ruo-Han; Zhou, Xiao-Feng; Duan, Wenhui et al. · Nat Commun · 2025

basic_science · Level V

Where this comes from

Abstract

Layered van der Waals transition metal dichalcogenides (TMDCs), generally composed of three atomic X-M-X planes in each layer (M = transition metal, X = chalcogen), provide versatile platforms for exploring diverse quantum phenomena. In each MX<sub>2</sub> layer, the M-X bonds are predominantly covalent in nature and, as a result, the cleavage of TMDC crystals normally occurs between the layers. Here we report the controllable realization of fractional-layer WTe<sub>2</sub> via an in-situ scanning tunneling microscopy (STM) tip manipulation technique. By applying STM tip pulses, hundreds of the topmost Te atoms are removed to form a nanoscale monolayer Te pit in the 1 T'-WTe<sub>2</sub>, thus realizing a 2/3-layer WTe<sub>2</sub> film. Such a configuration undergoes a spontaneous atomic reconstruction, yielding a unidirectional charge density redistribution with the wavevector and geometry quite distinct from that of pristine 1 T'-WTe<sub>2</sub>. Our results expand the conventional understanding of the TMDCs and are expected to stimulate further research on the structure and properties of fractional-layer TMDCs.