Jiang Chongyun, Liu Fucai, Cuadra Jorge, Huang Zumeng, Li Ke, Rasmita Abdullah, Srivastava Ajit, Liu Zheng, Gao Wei-Bo
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore.
Center for Programmable Materials, School of Materials Science & Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore.
Nat Commun. 2017 Oct 6;8(1):802. doi: 10.1038/s41467-017-00927-4.
Atomically thin monolayer transition metal dichalcogenides possess coupling of spin and valley degrees of freedom. The chirality is locked to identical valleys as a consequence of spin-orbit coupling and inversion symmetry breaking, leading to a valley analog of the Zeeman effect in presence of an out-of-plane magnetic field. Owing to the inversion symmetry in bilayers, the photoluminescence helicity should no longer be locked to the valleys. Here we show that the Zeeman splitting, however, persists in 2H-MoTe bilayers, as a result of an additional degree of freedom, namely the layer pseudospin, and spin-valley-layer locking. Unlike monolayers, the Zeeman splitting in bilayers occurs without lifting valley degeneracy. The degree of circularly polarized photoluminescence is tuned with magnetic field from -37% to 37%. Our results demonstrate the control of degree of freedom in bilayer with magnetic field, which makes bilayer a promising platform for spin-valley quantum gates based on magnetoelectric effects.Monolayer transition metal dichalcogenides host a valley splitting in magnetic field analogous to the Zeeman effect. Here, the authors report that the Zeeman splitting still persists in bilayers of MoTe without lifting the valley degeneracy, due to spin-valley-layer coupling.
原子级薄的单层过渡金属二硫属化物具有自旋和能谷自由度的耦合。由于自旋轨道耦合和空间反演对称性破缺，手性被锁定到相同的能谷，导致在存在面外磁场时出现能谷类似塞曼效应的现象。由于双层结构中的空间反演对称性，光致发光的螺旋性不应再被锁定到能谷。然而在此我们表明，由于一个额外的自由度，即层赝自旋，以及自旋-能谷-层锁定，塞曼分裂在2H-MoTe双层结构中仍然存在。与单层不同，双层中的塞曼分裂发生时不会解除能谷简并。圆偏振光致发光的程度随磁场从-37%调节到37%。我们的结果展示了利用磁场对双层结构中自由度的控制，这使得双层成为基于磁电效应的自旋-能谷量子比特的一个有前景的平台。单层过渡金属二硫属化物在磁场中存在类似于塞曼效应的能谷分裂。在此，作者报道由于自旋-能谷-层耦合，塞曼分裂在MoTe双层结构中仍然存在且不会解除能谷简并。
