Charge Instability in Single-Layer TiTe2 Mediated by van-der-Waals Bonding to Substrates
Meng-Kai Lin1*, Joseph A. Hlevyack2,5, Peng Chen3, Ro-Ya Liu2, Sung-Kwan Mo4, T.-C. Chiang1,2
1Physics, National Central University, Taoyuan, Taiwan
2Physics, University of Illinois at Urbana-Champaign, Illinois, USA
3School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China
4Advanced Light Source, Lawrence Berkeley National Laboratory, California, USA
5Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Illinois, USA
* Presenter:Meng-Kai Lin,
Single layers of transition metal dichalcogenides (TMDCs) are of interest for their emergent properties at the two-dimensional limit. However, the role of substrate effects is rarely discussed. For van-der-Waals bonding to an incommensurate substrate, the interaction can be expected to be weak, but is it negligible? Here, we report an experimental study of a model system to address this issue. The charge instability in a single-layer TiTe2 grown on PtTe2 films is examined as a function of the thickness of PtTe2 films, which are themselves grown on a bilayer-graphene-terminated SiC substrate. The results show that the (2x2) charge density wave in single-layer TiTe2 is strongly suppressed by increasing the film thickness of PtTe2. Given the interfacial bonding remains of the weak incommensurate van-der-Waals type, the observed changes are correlated with a thickness-dependent metallicity transformation in the PtTe2 substrate (from a wide-gap semiconductor to a semimetal). The results illustrate the crucial role of the substrate in single-layer physics.

Keywords: van der Waals, Transition metal dichalcogenide, Band structure, Photoemission, Single layer