Intercalation induced quasi-freestanding layer in TiSe$_2$

TL;DR

This study uses photoemission spectroscopy and theoretical calculations to show that potassium intercalation creates a quasi-freestanding TiSe2 layer with tunable electronic properties and suppressed lattice distortion.

Contribution

It demonstrates the formation of a quasi-freestanding TiSe2 layer via potassium intercalation and its impact on electronic structure and lattice distortion, supported by experimental and theoretical analysis.

Findings

Observation of conduction band splitting into two branches

Suppression of periodic lattice distortion upon doping

Confirmation of quasi-freestanding layer formation

Abstract

Angle-resolved photoemission spectroscopy is employed to study the electronic structure of bulk TiSe2 before and after doping with potassium impurities. A splitting in the conduction band into two branches is observed after room-temperature deposition. The splitting energy increases to approximately 130 meV when the sample is cooled to 40 K. One branch exhibits a non-dispersive two-dimensional feature, while other one shows the characteristics of three dimensional bulk band dispersion. Core level spectroscopy suggests that the K impurities predominantly occupy the intercalated sites within the van derWaals gap. The results indicate the formation of a quasi-freestandingTiSe2 layer. Additionally, doping completely suppresses the periodic lattice distortion in the surface region. These findings are further supported by density functional theory calculations, which compare the band structure of monolayer and bulk TiSe2 with experimental data. Thus, the dimensional and intrinsic electronic properties of 1T-TiSe2 can be controlled through the intercalation procedure used in this work.