Strong-coupling charge density wave in monolayer TiSe <sub>2</sub>
Matthew D. Watson, Akhil Rajan, Tommaso Antonelli, Kaycee Underwood, Igor Marković, Federico Mazzola, Oliver J. Clark, Gesa-R. Siemann, Deepnarayan Biswas, A. T. Hunter, Sven Jandura, Janika Reichstetter, Martin McLaren, Patrick Le Fèvre, Giovanni Vinai, P. D. C. King
Abstract
Abstract We study the 2 × 2 charge density wave (CDW) in epitaxially-grown monolayer TiSe 2 . 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.