Realization of Multiple Charge-Density Waves in NbTe2 at the Monolayer Limit

• Published in: Nano letters Vol. 23; no. 6; pp. 2107 - 2113
• Main Authors: Bai, Yusong, Jian, Tao, Pan, Zemin, Deng, Jinghao, Lin, Xiaoyu, Zhu, Chao, Huo, Da, Cheng, Zhengbo, Liu, Yong, Cui, Ping, Zhang, Zhenyu, Zou, Qiang, Zhang, Chendong
• Format: Journal Article
• Language: English
• Published: American Chemical Society 22-03-2023
• Subjects: molecular beam epitaxy; monolayer 1T-NbTe2; scanning tunneling microscopy and spectroscopy; charge-density waves
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.2c04306

Layered transition-metal dichalcogenides down to the monolayer (ML) limit provide a fertile platform for exploring charge-density waves (CDWs). Here, we experimentally unveil the richness of the CDW phases in ML-NbTe2 for the first time. Not only the theoretically predicted 4 × 4 and 4 × 1 phases but also two unexpected 28 × 28 and 19 × 19 phases are realized. For such a complex CDW system, we establish an exhaustive growth phase diagram via systematic efforts in the material synthesis and scanning tunneling microscope characterization. Moreover, the energetically stable phase is the larger-scale order ( 19 × 19 ), which is surprisingly in contradiction to the prior prediction (4 × 4). These findings are confirmed using two different kinetic pathways: i.e., direct growth at proper growth temperatures (T) and low-T growth followed by high-T annealing. Our results provide a comprehensive diagram of the “zoo” of CDW orders in ML-NbTe2.