Fang Zheyu's team from the School of Physics, Peking University recently proposed a new tungsten diselenide (WSe₂) valley-polarized electron beam manipulation method based on nano-antennas, which could use ultra-high resolution electron beams to manipulate metal plasmons to control the valley polarization of low-dimensional quantum materials.

This research provides a near-field excitation methodology of valley polarization, which offers exciting opportunities for deep-subwavelength valleytronics investigation, optoelectronic circuits integration and future quantum information technologies. Related research results are published in Nature Communications.

Valley pseudospin in transition metal dichalcogenides monolayers intrinsically provides the additional possibility to control valley carriers, raising a great impact on valleytronics in the following years. The spin-valley locking directly contributes to optical selection rules which allow for valley-dependent addressability of excitons by helical optical pumping.

As a binary photonic addressable route, manipulation of valley polarization states is indispensable while effective control methods at a deep-subwavelength scale are still limited. Researchers from Peking University report the excitation and control of valley polarization in h-BN/ WSe₂/h-BN and Au nanoantenna hybrid structure by the electron beam.

Near-field circularly polarized dipole modes can be excited via precise stimulation and generate the valley polarized cathodoluminescence via near-field interaction. Effective manipulation of valley polarization degree can be realized by variation of excitation position.

As an intrinsic characteristic related to the extreme value of the energy band structure of semiconductor materials, valley pseudospin provides additional freedom to regulate the behavior of carriers in specific energy valleys, and is expected to become a new generation of information carriers. Single-layer two-dimensional transition metal dichalcogenides (TMDs) materials, due to their naturally broken lattice reversal symmetry, leading to the coupling of spin and energy valleys, Cemented Carbide Drill Bits which enables researchers to selectively excite energy valleys through externally polarized light fields.

Among TMDs materials, single-layer WSe₂ is one of the van der Waals layered semiconductors with a direct bandgap, relatively large binding energy and high carrier mobility. Compared with MoS2, single-layer WSe₂ has stronger spin-orbit coupling, that is, it has the potential of long-term valley polarization, indicating that WSe₂ is an important material for valley electron and quantum information transmission.

However, there is no report on the composite structure of metal nanostructures and TMDs materials. How to accurately characterize and manipulate the electromagnetic field of metal structures on the carrier behavior in single-layer tungsten carbide burrs TMDs materials, especially the effect of valley pseudospins, is a difficult point in current research.

The Peking University research team designed a symmetrical nano-antenna and a metal/dielectric composite nano-structure of hexagonal boron nitride, WSe₂ and hexagonal boron nitride, using the ultra-high resolution characteristics of incident electron beams to precisely exciting the circle of the metal nano-antenna. The polarization dipole electromagnetic mode realizes the control of valley polarization of low-dimensional materials at the nanometer scale through near-field interactions, and uses electron beam excitation site movement to achieve valley polarization "on" http://arthuryves.mee.nu/automotive_seating_market_volume_analysis_and_key_trends_2016

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