- Lin, Meng-Kai;
- Villaos, Rovi Angelo B;
- Hlevyack, Joseph A;
- Chen, Peng;
- Liu, Ro-Ya;
- Hsu, Chia-Hsiu;
- Avila, José;
- Mo, Sung-Kwan;
- Chuang, Feng-Chuan;
- Chiang, T-C
Platinum ditelluride (PtTe_{2}), a type-II Dirac semimetal, remains semimetallic in ultrathin films down to just two triatomic layers (TLs) with a negative gap of -0.36 eV. Further reduction of the film thickness to a single TL induces a Lifshitz electronic transition to a semiconductor with a large positive gap of +0.79 eV. This transition is evidenced by experimental band structure mapping of films prepared by layer-resolved molecular beam epitaxy, and by comparing the data to first-principles calculations using a hybrid functional. The results demonstrate a novel electronic transition at the two-dimensional limit through film thickness control.