Deep subwavelength control of valley polarized cathodoluminescence in h-BN/WSe2/h-BN heterostructure.

Liheng Zheng,Yongji Gong,Donglin Liu,Yu Li,Zheyu Fang,Han Zhang,Meiling Jiang,Bo Shen,Feng Lin,Xingguo Wang,Xing Zhu,Zhixin Liu

doi:10.1038/s41467-020-20545-x

Abstract

Valley pseudospin in transition metal dichalcogenides monolayers intrinsically provides additional possibility to control valley carriers, raising a great impact on valleytronics in 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 deep-subwavelength scale are still limited. Here, we report the excitation and control of valley polarization in h-BN/WSe2/h-BN and Au nanoantenna hybrid structure by 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. This report 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.

Highlights

Valley pseudospin in transition metal dichalcogenides monolayers intrinsically provides additional possibility to control valley carriers, raising a great impact on valleytronics in following years
As an intrinsic property related to the extrema in band structure, provides an additional and unique degree of freedom to control behavior of carriers occupied in a specific valley, which is widely known as valleytronics[1,2]
The heterostructure of h-BN/WSe2/h-BN was prepared via a series of transfer processes. h-BN flakes were mechanically exfoliated from bulk h-BN and picked up in sequence by van der Waals force

Summary

Introduction

Valley pseudospin in transition metal dichalcogenides monolayers intrinsically provides additional possibility to control valley carriers, raising a great impact on valleytronics in following years. Limited by optical spatial resolution, the deep-subwavelength excitation and manipulation of valley polarization in 2D materials especially in WSe2 monolayer are less reported while such investigation is necessary for revealing physical nature of valley polarization as well as prospective compact valleytronic circuits. Metallic nanostructures represent a versatile platform in modern photonics study that is capable of generating and manipulating electromagnetic field It has been extensively investigated over the last decade owing to its enhanced local field, prominent control of optical properties and broad spectral responses from ultraviolet to infrared which is dominantly determined by surface plasmon resonance (SPR). Optical nanoantenna with plasmonic circular dipole mode has the possibility to address distinct valleys through near-field interaction with valley materials especially WSe2 monolayer, following optical selection rules

Methods

Results

Conclusion