Unveiling the Charge Density Wave Inhomogeneity and Pseudogap State in 1T-TiSe2

TL;DR

This study uses STM/STS to explore how doping affects the electronic inhomogeneity, pseudogap formation, and charge density wave behavior in 1T-TiSe2, revealing the complex interplay influencing its superconducting properties.

Contribution

It provides new insights into how lattice distortion and doping electrons influence the CDW and pseudogap states in 1T-TiSe2, highlighting their roles in superconductivity.

Findings

Lattice distortion reduces the CDW gap while maintaining 2x2 modulation.

Doping electrons promote pseudogap formation.

Pseudogap may serve as a precursor to superconductivity.

Abstract

By using scanning tunneling microscopy (STM) / spectroscopy (STS), we systematically characterize the electronic structure of lightly doped 1T-TiSe2, and demonstrate the existence of the electronic inhomogeneity and the pseudogap state. It is found that the intercalation induced lattice distortion impacts the local band structure and reduce the size of the charge density wave (CDW) gap with the persisted 2x2 spatial modulation. On the other hand, the delocalized doping electrons promote the formation of pseudogap. Domination by either of the two effects results in the separation of two characteristic regions in real space, exhibiting rather different electronic structures. Further doping electrons to the surface confirms that the pseudogap may be the precursor for the superconducting gap. This study suggests that the competition of local lattice distortion and the delocalized doping effect contribute to the complicated relationship between charge density wave and superconductivity for intercalated 1T-TiSe2.