Imaging two-component nature of Dirac-Landau levels in the topological surface state of Bi2Se3

TL;DR

This study visualizes and analyzes the two-component wave function of Dirac electrons in the topological surface state of Bi2Se3, revealing potential-induced Landau level splitting and spin textures with implications for spin manipulation.

Contribution

It provides direct spectroscopic imaging evidence of the two-component nature of Landau levels in a topological insulator and introduces a model explaining their internal structures and spin textures.

Findings

Observation of Landau level splitting due to Coulomb potential

Visualization of internal Landau orbit structures

Prediction of energy-dependent spin-magnetization textures

Abstract

Massless Dirac electrons in condensed matter have attracted considerable attention. Unlike conventional electrons, Dirac electrons are described in the form of two-component wave functions. In the surface state of topological insulators, these two components are associated with the spin degrees of freedom, hence governing the magnetic properties. Therefore, the observation of the two-component wave function provides a useful clue for exploring the novel spin phenomena. Here we show that the two-component nature is manifested in the Landau levels (LLs) whose degeneracy is lifted by a Coulomb potential. Using spectroscopic-imaging scanning tunneling microscopy, we visualize energy and spatial structures of LLs in a topological insulator Bi2Se3. The observed potential-induced LL splitting and internal structures of Landau orbits are distinct from those in a conventional electron system and are well reproduced by a two-component model Dirac Hamiltonian. Our model further predicts non-trivial energy-dependent spin-magnetization textures in a potential variation. This provides a way to manipulate spins in the topological surface state.