Highly persistent spin textures with giant tunable spin splitting in the two-dimensional germanium monochalcogenides

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Controlling spin textures in semiconductors is crucial for developing advanced spintronic devices.
• Identifying materials with persistent spin texture (PST) is a significant challenge.
• PST preserves unidirectional spin orientation in momentum space, potentially leading to long carrier spin lifetimes.

Purpose of the Study:

• To investigate the emergence of PST in two-dimensional (2D) germanium monochalcogenides (GeMC).
• To analyze PST in both pure GeX and Janus Ge2XY monolayers.
• To explore the tunability of PST through strain and its implications for spintronic applications.

Main Methods:

• Utilizing first-principles density functional theory calculations.
• Examining two stable formations of 2D GeMC: pure GeX and Janus Ge2XY monolayers.
• Analyzing the spin orientation and spin-orbit coupling (SOC) parameters.

Main Results:

• Confirmed the presence of PST around the valence band maximum in 2D GeMC.
• Observed out-of-plane PST in pure GeX (C2v symmetry) and canted PST in Janus Ge2XY (Cs symmetry).
• Found a large SOC parameter sustaining PST, tunable by in-plane strain, leading to a small spin polarization wavelength.

Conclusions:

• 2D germanium monochalcogenides exhibit PST, offering a promising platform for spintronics.
• The PST's characteristics are dependent on the crystal's point group symmetry.
• Tunable large SOC in these materials is beneficial for developing short spin channels in devices like spin Hall transistors.