Transition from Optically Excited to Intrinsic Spin Polarization in WSe_{2}.

Area of Science:

• Condensed matter physics
• Materials science
• Nanotechnology

Background:

• Layered 2D van der Waals materials, including transition metal dichalcogenides like WSe2, show significant promise for spintronic and optoelectronic devices.
• Understanding the behavior of optically excited spin and charge carriers is crucial for realizing the full potential of these materials.
• Investigating the interplay between excited spin polarization and the intrinsic spin texture of conduction bands is a key challenge.

Purpose of the Study:

• To investigate the spin polarization of conduction bands in bulk tungsten diselenide (WSe2).
• To understand the dynamics of optically excited spin carriers and their alignment with the material's intrinsic spin texture.
• To explore the role of electron doping and intervalley scattering in spin transport.

Main Methods:

• Utilized static and time-resolved spin-resolved photoemission spectroscopy to probe WSe2.
• Employed electron doping to reveal intrinsic spin polarization.
• Performed photocurrent calculations to complement experimental findings.

Main Results:

• Electron doping successfully revealed the intrinsic spin polarization of the conduction bands.
• Time-resolved measurements tracked the dynamic evolution of excited spin carriers.
• Intervalley scattering was identified as a spin-conserving process.
• Spin transport was observed to align with the intrinsic conduction band spin polarization after approximately 150 femtoseconds.

Conclusions:

• The study elucidates the spin dynamics in WSe2, demonstrating the alignment of photoexcited carriers with intrinsic spin polarization.
• Findings provide critical insights into spin transport mechanisms in 2D materials, essential for spintronic applications.
• The spin-conserving nature of intervalley scattering highlights WSe2's potential for efficient spin manipulation.