Title: Valley selective optical control of excitons in 2D semiconductors using Chiral metasurface Show Chinese title

Title: 使用手性超表面对二维半导体中激子的谷选择性光学控制

Abstract: Recent advances in condensed matter physics have shown that the valley degree of freedom of electrons in 2D materials with hexagonal symmetry, such as graphene, h-BN, and TMDs, can be efficiently exploited, leading to the emergent field of valleytronics, which offers unique opportunities for efficient data transfer, computing and storage. The ability to couple the valley degree of freedom of electrons with light can further expand the ways one manipulate this degree of freedom, thus envisioning a new class of solid-state-photonic interfaces and devices. Besides this expansion of control of valley by light-waves, coupling of photons with valley-polarized electrons can dramatically expand the landscape of available optical responses, which may bring new means of controlling light in photonic devices. In this work we design such hybrid solid-state photonic metasurface integrating 2D TMD and photonic all-dielectric metasurface. While TMD is naturally endowed with the property of valley to optical-polarization coupling, the photonic metasurface is designed to produce chiral field which selectively couples to the valley degree of freedom of solid-state TMD component. We experimentally demonstrate that such coupling leads to controlled valley polarization due to the coupling of 2D materials with the chiral photonic metasurface. The measured emission from valley excitons in this hybrid system yields the preferential emission of specific helicity. Show Chinese abstract

Abstract: 最近在凝聚态物理领域的进展表明，具有六方对称性的二维材料（如石墨烯、h-BN和TMDs）中电子的谷自由度可以被有效利用，从而催生了谷电子学这一新兴领域，该领域为高效的数据传输、计算和存储提供了独特的机会。 将电子的谷自由度与光耦合的能力可以进一步扩展操纵这一自由度的方式，从而设想一类新的固态-光子接口和器件。 除了通过光波扩展对谷的控制外，光子与谷极化电子的耦合可以显著扩展可用的光学响应范围，这可能为光子器件中控制光提供新的手段。 在这项工作中，我们设计了一种混合的固态光子超表面，集成了二维TMD和光子全介质超表面。 虽然TMD天然具备谷与光学极化耦合的特性，但光子超表面被设计成产生手性场，该场选择性地与固态TMD组件的谷自由度耦合。 我们实验上证明，这种耦合由于二维材料与手性光子超表面的耦合导致了受控的谷极化。 在这种混合系统中，谷激子的发射测量结果显示出特定螺旋度的优先发射。