Intra- and Interband Electron Scattering in the Complex Hybrid Topological Insulator Bismuth Bilayer on Bi$_2$Se$_3$

TL;DR

This study uses low-temperature spectroscopy and simulations to analyze electron scattering in a bismuth bilayer on Bi2Se3, revealing complex inter- and intraband processes, electron transfer effects, and the positioning of topological states.

Contribution

It provides a detailed experimental and theoretical analysis of electron scattering and band structure in a hybrid topological insulator system, highlighting electron transfer and spin-splitting phenomena.

Findings

Intraband scattering occurs in the bilayer valence band and Bi2Se3 conduction band.

Interband scattering involves the topological state and bilayer valence band.

The bilayer band gap is shifted above the Fermi level due to electron transfer.

Abstract

The band structure, intra- and interband scattering processes of the electrons at the surface of a bismuth-bilayer on Bi$_2$Se$_3$ have been experimentally investigated by low-temperature Fourier-transform scanning tunneling spectroscopy. The observed complex quasiparticle interference patterns are compared to a simulation based on the spin-dependent joint density of states approach using the surface-localized spectral function calculated from first principles as the only input. Thereby, the origin of the quasiparticle interferences can be traced back to intraband scattering in the bismuth bilayer valence band and Bi$_2$Se$_3$ conduction band, and to interband scattering between the two-dimensional topological state and the bismuth-bilayer valence band. The investigation reveals that the bilayer band gap, which is predicted to host one-dimensional topological states at the edges of the bilayer, is pushed several hundred milli-electronvolts above the Fermi level. This result is rationalized by an electron transfer from the bilayer to Bi$_2$Se$_3$ which also leads to a two-dimensional electron state in the Bi$_2$Se$_3$ conduction band with a strong Rashba spin-splitting, coexisting with the topological state and bilayer valence band.