MoWSe_Spin and pseudospin properties of energetically controllable dark and bright excitons in tailored Mo1-xWxSe2 alloys

二维过渡金属二硫属化物，其层状结构允许即使在室温下也存在异常强烈的束缚激子，具有独特的自旋和谷赝自旋特征，这可能会引起纳米光子学以及基于自旋的纳米电子学的高度令人兴奋和新颖的物理。为了充分利用这种新材料体系的潜力，并使人们能够定制这些纳米材料的功能和结构特性，必须解决其单层中激子的关键问题，为此，我们重点研究了新型Mo 1-xWxSe 2合金中光学亮和暗K谷激子之间的相互作用。这些机械剥离的合金的组合物的依赖性，使我们能够调整的A-和B-激子自旋状态的能量，也导致暗和亮激子混合，在很宽的范围内。使用可调导带和价带水平的Mo 1-xWxSe 2结构，我们希望提供新的和彻底的见解自旋和谷赝自旋的性质和动力学，这将是关于可调激子和载流子交换相互作用和自旋轨道耦合以及激子与周围浴的相互作用进行研究。后者不仅应包括核自旋和声子，而且还包括缺陷，衬底材料和单层几何形状。光学检测磁共振技术结合共振和偏振激光激发和微米空间分辨率将允许基于自旋的激子属性的磁共振成像，从而向基于自旋的量子信息器件和传感器技术迈出一步。除了暗激子和亮激子能量的成分依赖可控性之外，我们还将对衬底材料施加单向和双向应变，以微调自旋状态能量，操纵电子特别是空穴的自旋轨道耦合，并改变对称条件。的K-和γ-谷激子的比较研究将进一步提高自旋和多载流子物理的理解，通过利用高能量激光激发可变功率，在定制的Mo 1-xWxSe 2结构。

Two-dimensional transition metal dichalcogenides, whose layered structure allows for unusually strongly bound excitons existing even at room temperature, possess unique spin and valley pseudospin features that may give rise to highly exciting and novel physics for the nanophotonics as well as spin-based nanoelectronics. In order to exploit the full potential of this new material system and to allow one to tailor the functional and structural properties of these nanomaterials, key open questions regarding the excitons in their monolayers have to be answered.For that purpose, we focus on the interaction between optically bright and dark K-valley excitons in novel Mo1-xWxSe2 alloys. The composition dependence of these mechanically exfoliated alloys shall allow us to tune the energies of the A- and B-exciton spin states, also leading to a dark- and bright-exciton mixing, in a wide range. Using the Mo1-xWxSe2 structures with tunable conduction- and valence-band levels, we expect to provide novel and thorough insights into the spin and valley pseudospin properties and dynamics, which shall be studied with regard to the tunable exciton and carrier exchange interactions and spin-orbit coupling as well as to the interaction of the excitons with the surrounding bath. The latter shall include not only nuclear spins and phonons, but also defects, substrate materials and the monolayer geometry. Optically detected magnetic resonance techniques combined with resonant and polarized laser excitation and micrometer spatial resolution shall allow for a magnetic resonance imaging of the spin-based exciton properties, thus making a step toward spin-based quantum information devices and sensor technologies. Besides the composition-dependent controllability of the dark and bright exciton energies, we will apply uni- and biaxial strain to the substrate material for fine-tuning the spin state energies, manipulating the spin-orbit coupling of the electrons and particularly holes and changing symmetry conditions. A comparative study of the K- and Gamma-valley excitons shall furthermore enhance the understanding of spin and many-carrier physics, by exploiting high-energy laser excitation with variable power, in the tailored Mo1-xWxSe2 structures.