The free-standing monolayer Si2Te2 (ML-Si2Te2) has been theoretically predicted to host a room-temperature quantum spin Hall phase. However, its experimental realization remains challenge due to the absence of a three-dimensional counterpart. Here, we demonstrate that HfTe2 serves as an ideal substrate for the epitaxial growth of ML-Si2Te2, preserving its topological phase. Scanning tunneling microscopy and spectroscopy confirm a strain-free (1×1) lattice of ML-Si2Te2, along with a sizable band gap, which is well captured by first-principles calculations. Moreover, distinct edge states, independent of step geometry and exhibiting a broad spatial distribution, are observed at ML-Si2Te2 step edges, underscoring its topological nature.
@article{arxiv.2508.07351,
title = {Experimental Realization of the Topologically Nontrivial Phase in Monolayer Si$_2$Te$_2$},
author = {Xiaochun Huang and Lingxiao Zhao and Rui Xiong and Wenbin Li and Bao-tian Wang and Baisheng Sa and Matthias Bode},
journal= {arXiv preprint arXiv:2508.07351},
year = {2025}
}