Spin-orbit coupling in nearly metallic chiral carbon nanotubes: a density-functional based study

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Chemistry

Background:

• Spin-orbit interaction (SOI) in carbon nanotubes (CNTs) is a complex phenomenon with ongoing theoretical and experimental investigations.
• Previous studies have explored various aspects of SOI in CNTs, but a comprehensive theoretical approach remains crucial.

Purpose of the Study:

• To develop and present an accurate implementation of spin-orbit interactions in a density-functional theory (DFT) framework for carbon nanotubes.
• To investigate the spin-splitting of frontier bands in both armchair and chiral carbon nanotubes, considering core and valence orbital contributions.

Main Methods:

• Implementation of a comprehensive density-functional theory (DFT) framework incorporating both core and valence orbital contributions to spin-orbit interactions.
• Systematic analysis of spin-splitting in armchair nanotubes as a function of diameter.
• Detailed examination of band splitting in chiral nanotubes, varying diameter and chiral angle.

Main Results:

• Calculated spin-splitting of frontier bands in armchair nanotubes to be on the order of several micro-electronvolts (μeV).
• Observed that the spin-splitting in armchair nanotubes shows minimal dependence on the nanotube diameter.
• Provided a systematic analysis of band splitting in chiral nanotubes, correlating it with diameter and chiral angle, showing good agreement with existing data.

Conclusions:

• The accurate DFT implementation successfully captures spin-orbit interactions in carbon nanotubes, including atomic and global contributions.
• The findings provide valuable insights into the spin properties of carbon nanotubes, relevant for spintronic applications.
• The methodology's ability to encode topological effects like helical symmetry is significant for understanding chirality-induced spin selectivity (CISS).