Surface state photoelectrons in topological insulators: Green's function approach.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Topological insulators possess unique surface states with linear energy dispersion and chirality.
• Understanding electron behavior in these states is crucial for novel electronic and spintronic applications.
• Photoemission spectroscopy is a key technique for probing surface electronic properties.

Purpose of the Study:

• To compute photoemission intensity and polarization for surface states in topological insulators.
• To investigate the role of chirality, energy dispersion, and tunneling amplitude on electron-photon coupling.
• To analyze spin textures using a chiral Dirac Hamiltonian under various conditions (helical, Zeeman, warping).

Main Methods:

• Utilized a chiral Dirac Hamiltonian to model surface states.
• Employed the Green's function formalism to derive exact results for photoemission.
• Analyzed photoemission to second order in the laser field intensity.

Main Results:

• Photoemission intensity is sensitive to laser coherent state intensity.
• Photoelectron polarization depends on the surface topology of electronic states and photon polarization.
• Effective electron-photon coupling is normalized by the tunneling amplitude into the vacuum.

Conclusions:

• The study provides a theoretical framework for understanding photoemission from topological insulator surface states.
• Results highlight the sensitivity of photoemission to both external fields and intrinsic material properties.
• This work offers insights into controlling and detecting spin textures in topological materials.