Compelling evidence suggests distinct correlated electron behavior may exist only in clean 2D materials such as 1T-TaS2. Unfortunately, experiment and theory suggest that extrinsic disorder in free standing 2D layers disrupts correlation-driven quantum behavior. Here we demonstrate a route to realizing fragile 2D quantum states through endotaxial polytype engineering of van der Waals materials. The true isolation of 2D charge density waves (CDWs) between metallic layers stabilizes commensurate long-range order and lifts the coupling between neighboring CDW layers to restore mirror symmetries via interlayer CDW twinning. The twinned-commensurate charge density wave (tC-CDW) reported herein has a single metal--insulator phase transition at ~350 K as measured structurally and electronically. Fast in-situ transmission electron microscopy and scanned nanobeam diffraction map the formation of tC-CDWs. This work introduces endotaxial polytype engineering of van der Waals materials to access latent 2D ground states distinct from conventional 2D fabrication.
@article{arxiv.2102.09079,
title = {Two-dimensional charge order stabilized in clean polytype heterostructures},
author = {Suk Hyun Sung and Noah Schnitzer and Steve Novakov and Ismail El Baggari and Xiangpeng Luo and Jiseok Gim and Nguyen M. Vu and Zidong Li and Todd B. Brintlinger and Yu Liu and Wenjian Lu and Yuping Sun and Parag Deotare and Kai Sun and Liuyan Zhao and Lena F. Kourkoutis and John T. Heron and Robert Hovden},
journal= {arXiv preprint arXiv:2102.09079},
year = {2023}
}