Spin and Valley Dynamics in 2D van der Waals Materials

层状货车德瓦耳斯（vdW）材料的成功研究开辟了许多新的研究方向和潜在的应用。这里，单层（ML）MoS 2、MoSe 2、WS 2和WSe 2的多功能性由于位于布里渊区的K点处的可见光谱区域中的直接带隙而突出。除了二维光电子学的前景，ML过渡金属二硫属化物（TMDC）是有趣的利用自旋和谷赝自旋的电子和空穴在（量子）信息处理的潜在应用。信息不仅可以通过电子（或空穴）是否向上或向下自旋来编码，而且还可以通过它是否位于K+或K-谷来编码。强自旋轨道耦合分离自旋态和晶体的不对称性导致谷特定的光学选择规则。因此，可以选择性地填充K+或K-谷，并使用偏振光进行探测。LPCNO图卢兹- LU汉诺威联合会将广泛研究ML TMDC中自旋和谷动力学的内在时间尺度以及控制自旋和谷极化稳定性的机制。双方合作伙伴已经成功地在全光自旋噪声光谱（SNS）领域开展了共同的研究项目。我们专注于长寿命的激发与稳定的自旋和谷态和初始化自旋和谷极化光学空穴和电子掺杂的样品。掺杂是通过化学方法或在LPCNO已经运行的门控结构中实现的。我们将通过3种不同的技术研究和调整自旋动力学：a）时间分辨光致发光测量将监测带电激子（trion）辐射寿命期间的极化动力学和转移，包括自旋禁戒（暗）trion的作用。B）通过采用汉诺威开发的泵浦探测测量，我们将探测复合后驻留载流子的自旋和谷极化。c）我们的目标是第一次在TMDC上执行SNS，从而获得载流子的长期内在极化动力学，其关键优势是在热平衡时获得完整的时间动力学。LUH小组是这一领域的世界领导者，将研究不同载流子浓度下从n型到p型样品的主要去极化机制。高品质的样品可用于该财团与光学过渡线宽接近均匀的限制，在LPCNO制造的封装样品。我们将研究自旋分裂在符号和大小上都不同的不同合金和材料。我们将调查的极化动力学的本地化的作用，从2D限制在ML到0 D限制的缺陷。我们将测量vdW异质结构中的极化和电荷转移动力学。在这里，我们的目标是通过利用不同TMDC材料的能带对准，在真实的或动量空间中直接或间接的载流子复合之间切换。

The extremely successful research on layered van der Waals (vdW) materials opened up many new research-lines and potential applications. Here, the versatility of monolayer (ML) MoS2, MoSe2, WS2, and WSe2 stands out due to the direct-bandgap in the visible spectral region located at the K-points of the Brillouin zone. Besides their promise for 2D opto-electronics, ML transition metal dichalcogenides (TMDCs) are interesting for exploiting both the spin and valley pseudospin of electrons and holes for potential applications in (quantum) information processing. The information may be encoded not only by whether an electron (or hole) has spin up or down, but also if it resides in the K+ or K- valley. Strong spin-orbit coupling separates the spin states and crystalline asymmetry leads to valley specific optical selection rules. Thus K+ or K- valleys can be selectively populated and probed using polarized light. The consortium LPCNO Toulouse - LU Hannover will extensively investigate the intrinsic timescales of spin and valley dynamics in ML TMDCs and the mechanisms governing the stability of spin and valley polarization. Both partners have already successfully conducted common research projects in the field of all optical spin noise spectroscopy (SNS). We focus on longer-lived excitations with stable spin and valley states and initialize spin and valley polarization optically for hole and electron doped samples. Doping is achieved chemically or in gated structures already operational at LPCNO. We will study and tune the spin dynamics by 3 different techniques: a) time resolved photoluminescence measurements will monitor the polarization dynamics and transfer during the radiative lifetime of the charged exciton (trion) including the role of spin-forbidden (dark) trions. b) By employing pump-probe measurements developed in Hannover we will probe the spin and valley polarization of resident carriers after recombination. c) For the first time we aim to perform SNS on TMDCs giving access to the long-term, intrinsic polarization dynamics of carriers with the key advantage of accessing the complete temporal dynamics at thermal equilibrium. The LUH group is a world leader in this field and will study the main depolarization mechanisms going from n- to p-type samples for varied carrier concentrations. High quality samples are available to the consortium with optical transition linewidth approaching the homogenous limit in encapsulated samples fabricated at LPCNO. We will study different alloys and materials with spin splittings varying in sign and magnitude. We will investigate the role of localization on the polarization dynamics by going from 2D confinement in MLs to 0D confinement on defects. We will measure the polarization and the charge transfer dynamics in vdW heterostructures. Here, we aim to switch between carrier recombination that is either direct or indirect in real- or momentum-space, by exploiting the band alignment of different TMDC materials.