Liu Sheng, Granados Del Águila Andrés, Liu Xue, Zhu Yihan, Han Yu, Chaturvedi Apoorva, Gong Pu, Yu Hongyi, Zhang Hua, Yao Wang, Xiong Qihua
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
Advance Membrane and Porous Materials Center, Division of Physical and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia.
ACS Nano. 2020 Aug 25;14(8):9873-9883. doi: 10.1021/acsnano.0c02703. Epub 2020 Aug 5.
Room-temperature manipulation and processing of information encoded in the electronic valley pseudospin and spin degrees of freedoms lie at the heart of the next technological quantum revolution. In atomically thin layers of transition-metal dichalcogenides (TMDs) with hexagonal lattices, valley-polarized excitations and valley quantum coherence can be generated by simply shining with adequately polarized light. In turn, the polarization states of light can induce topological Hall currents in the absence of an external magnetic field, which underlies the fundamental principle of opto-valleytronics devices. However, demonstration of optical generation of valley polarization at room temperature has remained challenging and not well understood. Here, we demonstrate control of strong valley polarization (valley quantum coherence) at of up to ∼50% (∼20%) by strategically designing Coulomb forces and spin-orbit interactions in atomically thin TMDs chalcogenide alloying. We show that tailor making the carrier density and the relative order between optically active (bright) and forbidden (dark) states by key variations on the chalcogenide atom ratio allows full control of valley pseudospin dynamics. Our findings set a comprehensive approach for intrinsic and efficient manipulation of valley pseudospin and spin degree of freedom toward realistic opto-valleytronics devices.
室温下对编码于电子能谷赝自旋和自旋自由度中的信息进行操控和处理，是下一次技术量子革命的核心所在。在具有六边形晶格的过渡金属二硫属化物（TMD）原子薄层中，通过简单地用适当偏振光照射，就可以产生谷极化激发和谷量子相干。反过来，在没有外部磁场的情况下，光的偏振态可以诱导拓扑霍尔电流，这是光谷电子器件的基本原理。然而，室温下光生谷极化的演示仍然具有挑战性，且尚未得到很好的理解。在这里，我们通过在原子薄的TMD硫族化物合金中策略性地设计库仑力和自旋轨道相互作用，证明了在高达约50%（约20%）的情况下对强谷极化（谷量子相干）的控制。我们表明，通过硫族化物原子比的关键变化来定制载流子密度以及光学活性（亮）态和禁戒（暗）态之间的相对顺序，可以完全控制谷赝自旋动力学。我们的研究结果为朝着实际的光谷电子器件对谷赝自旋和自旋自由度进行本征和高效操控设定了一种全面的方法。
