Strong-coupling charge density wave in monolayer TiSe2

We study the 2 x 2 charge density wave (CDW) in epitaxially-grown monolayer TiSe2. Our temperature-dependent angle-resolved photoemission spectroscopy measurements indicate a strong-coupling instability, but reveal how not all states couple equally to the symmetry-breaking distortion, with an electron pocket persisting to low temperature as a non-bonding state. We further show how the CDW order can be suppressed by a modest doping of around 0.06(2) electrons per Ti. Our results provide an opportunity for quantitative comparison with a realistic tight-binding model, which emphasises a crucial role of structural aspects of the phase transition in understanding the hybridisation in the ground state. Together, our work provides a comprehensive understanding of the phenomenology of the CDW in TiSe(2)in the 2D limit.

Automated summary

The study of 2 x 2 charge density wave in epitaxially-grown monolayer TiSe2 reveals a strong coupling instability and the existence of an electron pocket as a non-bonding state at low temperatures. It is shown that the CDW order can be suppressed with modest doping of around 0.06(2) electrons per Ti. The results provide a comprehensive understanding of the CDW phenomenology in TiSe2 in the 2D limit, emphasizing the crucial role of structural aspects in the phase transition for hybridization in the ground state.