Weyl fermion-based spin current generation (WeylSPIN)

由于其拓扑保护，螺旋自旋结构，Weyl半金属是有前途的电驱动自旋发生器。本项目旨在获得对两种ii型Weyl半金属WTe2和MoTe2的多层和单层自旋电流和自旋动力学的基本理解。为了完成这一任务，我们计划将磁输运光谱实验（可以产生自旋极化）与时间和空间分辨的螺旋光电流和电导测量（可以提供自旋弛豫时间）结合起来。通过获得在两组中研究的同一样品的自旋极化和弛豫时间，我们设想确定超薄薄片中晶体学方向依赖的自旋和电荷输运过程的相关“光电”时间和潜在散射机制。进一步的目标是确定体态和表面态对自旋电流产生的单独贡献，以及详细阐明两种可能的晶体相和单层数量的影响。在项目的后期阶段，我们打算展示一个基于Berry曲率的开关，通过静电栅极场产生自旋电流，同时评估相应的输运时间尺度和特征。

Owing to their topologically protected, helical spin texture, Weyl semimetals are promising as electrically driven spin generators. The present project aims at gaining a fundamental understanding of the spin currents and spin dynamics in multi- and monolayers of the two type-II Weyl semimetals WTe2 and MoTe2. To reach this task, we plan to combine magnetic transport spectroscopy experiments, which can yield the spin polarisation, with time- and spatially-resolved helical photocurrent and -conductance measurements, which can provide the spin relaxation times. By gaining access to both, spin polarisation and relaxation times for one-and-the-same samples studied in the two groups, we envision determining the relevant “optoelectronic” times and underlying scattering mechanisms for the crystallographic direction-dependent spin and charge transport processes in the ultrathin sheets. Further objectives are to identify the individual contributions of the bulk and surface states to the spin current generation, as well as to clarify in detail the influence of the two possible crystal phases and the number of monolayers. For the later project stage, we intend demonstrating a Berry curvature-based switching of the spin current generation by an electrostatic gate field, along with evaluating the corresponding transport time scales and signatures.