Hidden order revealed by light-driven Kerr rotation in Centrosymmetric bulk WSe₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Optics

Background:

• Single-layer transition-metal dichalcogenides are key for valleytronics due to broken inversion symmetry.
• Bulk materials with inversion symmetry were previously thought unsuitable for such applications.
• Exploiting quantum physics in bulk centrosymmetric materials presents a significant challenge.

Purpose of the Study:

• To investigate the possibility of generating optical Kerr rotation in bulk WSe2 without breaking point-inversion symmetry.
• To explore the underlying quantum mechanisms responsible for optical responses in bulk centrosymmetric materials.
• To demonstrate the potential of bulk WSe2 for novel optoelectronic and orbitronics applications.

Main Methods:

• Utilized circularly-polarized light to induce optical Kerr rotation in bulk WSe2.
• Performed spectral analysis to identify exciton features and understand their origins.
• Measured the Kerr response lifetime to elucidate excitonic dynamics.

Main Results:

• Achieved significant optical Kerr rotation in bulk WSe2 on ultrafast timescales, despite the presence of point-inversion symmetry.
• Identified distinct A-, B-, and C-exciton features attributed to hidden order and spin Berry curvature.
• Determined a Kerr response lifetime of approximately 500 fs, indicating dominant excitonic dynamics.

Conclusions:

• Hidden quantum orders in bulk centrosymmetric layered materials can manifest in observable bulk properties.
• Bulk WSe2 can be effectively utilized in advanced optoelectronic and orbitronics applications.
• The findings challenge previous assumptions about the limitations of bulk materials in valleytronics.