Pseudogap and dark states in quantum materials

Keun Su Kim

Pseudogap has been a long-standing issue in the study of strongly correlated electron systems. One of the exciting opportunities with two-dimensional (2D) quantum materials is their simplicity and tunable electronic band structures, for example, by surface doping. Indeed, surface doping has been employed to tune the band gap of black phosphorus over the energy range greater than its intrinsic band gap¹. This tunable band gap can also be used not only to deliberately induce the topological phase transition to the 2D Dirac semimetal state protected by spacetime inversion symmetry², but also to systematically trace the evolution of quantum phases (pseudospin) across the band inversion³. In this talk, I will introduce our recent angle-resolved photoemission spectroscopy study on the observation of band renormalizations and pseudogap by the short-range order (disorder) of dopants⁴. If time permits, I will also introduce our more recent study on dark states in the electronic structure of quantum materials with two pairs of sublattices⁵.

1. J. Kim et al., Science 349, 723 (2015).

2. J. Kim et al., Phys. Rev. Lett. 119, 226801 (2017).

3. S. W. Jung et al., Nature Mater. 19, 277 (2020). 

4. S. H. Ryu et al., Nature 596, 68 (2021).

5. Y. Chung et al., in review (2023).