Terahertz-driven hot Dirac fermion and plasmon dynamics in the bulk-insulating topological insulator Bi2Se3

Abstract

© 2022 American Physical Society.For degenerately doped three-dimensional topological insulators (3D TIs), the interaction dynamics between Dirac fermions and collective charge oscillations (plasmons) are considerably complicated. In particular, the low-energy contribution near band inversion is largely obscure because of the bulk-surface interaction as well as the two-dimensional electron gas (2DEG). We have circumvented these issues by performing high-field terahertz (THz) pump-probe spectroscopy in bulk insulating Bi2Se3 TI microribbon array structures. Plasmon blueshift of 11% was found to occur within 4 ps under 0.433 MV/cm THz excitation compared to the near-equilibrium state. Although the conventional optical pump or engineered microribbon TIs exhibits a similar plasmon blueshift, our observation is readily explained by the intrinsic plasmon behavior from the increased electronic temperature (Te≅1430K) and reduced chemical potential (μ≅16meV) without considering extrinsic contributions. Our findings may apply to other classes of Dirac materials to investigate the coupled low-energy interactions with collective quasiparticles.