Valley-Dependent Emission Patterns Enabled by Plasmonic Nanoantennas.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Optics

Background:

• Controlling emission patterns of valley-polarized excitons in transition metal dichalcogenides is crucial for advanced devices.
• Existing methods face challenges in linking routing effects to valley polarization and distinguishing them from optical scattering.

Purpose of the Study:

• To experimentally and numerically demonstrate a direct link between excitonic valley polarization and far-field emission patterns.
• To enable quantitative evaluation of valley-selective emission routing.
• To establish a robust platform for valleytronic signal processing.

Main Methods:

• Utilized gold nanobar dimer antennas to manipulate the angular emission pattern of monolayer tungsten diselenide at cryogenic temperatures.
• Employed excitation with opposite circularly polarized light to probe valley-selective asymmetry in photoluminescence circular dichroism.
• Developed a reciprocity-based numerical framework for modeling valley-selective emission in periodic systems.

Main Results:

• Observed a 2% valley-selective asymmetry in photoluminescence circular dichroism, confirming valley-dependent emission manipulation.
• Numerical calculations revealed that directionality is a symmetry-protected property of the nanoantenna array.
• Demonstrated that emitter distribution can substantially enhance valley-dependent directionality.

Conclusions:

• Established a direct correlation between excitonic valley polarization and emission patterns.
• Validated a nanoantenna platform for quantitative evaluation and manipulation of valley-selective emission.
• Showcased the potential of this platform for robust valleytronic signal processing and advanced optoelectronic devices.