Li Jia-Xin, Li Wei-Qing, Hung Sheng-Hsiung, Chen Po-Liang, Yang Yueh-Chiang, Chang Tian-Yun, Chiu Po-Wen, Jeng Horng-Tay, Liu Chang-Hua
Institute of Photonics Technologies, National Tsing Hua University, Hsinchu, Taiwan.
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
Nat Nanotechnol. 2022 Jul;17(7):721-728. doi: 10.1038/s41565-022-01115-2. Epub 2022 May 2.
Electrical manipulation of the valley degree of freedom in transition metal dichalcogenides is central to developing valleytronics. Towards this end, ferromagnetic contacts, such as Ga(Mn)As and permalloy, have been exploited to inject spin-polarized carriers into transition metal dichalcogenides to realize valley-dependent polarization. However, these materials require either a high external magnetic field or complicated epitaxial growth steps, limiting their practical applications. Here we report van der Waals heterostructures based on a monolayer WSe and an FeGeTe/hexagonal boron nitride ferromagnetic tunnelling contact that under a bias voltage can effectively inject spin-polarized holes into WSe, leading to a population imbalance between ±K valleys, as confirmed by density functional theory calculations and helicity-dependent electroluminescence measurements. Under an external magnetic field, we observe that the helicity of electroluminescence flips its sign and exhibits a hysteresis loop in agreement with the magnetic hysteresis loop obtained from reflective magnetic circular dichroism characterizations on FeGeTe. Our results could address key challenges of valleytronics and prove promising for van der Waals magnets for magneto-optoelectronics applications.
对过渡金属二硫族化合物中的谷自由度进行电学操控是发展谷电子学的核心。为此，诸如Ga(Mn)As和坡莫合金等铁磁接触已被用于将自旋极化载流子注入过渡金属二硫族化合物中，以实现谷依赖极化。然而，这些材料要么需要高外部磁场，要么需要复杂的外延生长步骤，这限制了它们的实际应用。在此，我们报道了基于单层WSe和FeGeTe/六方氮化硼铁磁隧道接触的范德华异质结构，在偏置电压下，该结构可有效地将自旋极化空穴注入WSe中，导致±K谷之间的载流子数失衡，这一点已通过密度泛函理论计算和与螺旋度相关的电致发光测量得到证实。在外部磁场下，我们观察到电致发光的螺旋度改变其符号，并呈现出一个磁滞回线，这与从FeGeTe的反射磁圆二色性表征获得的磁滞回线一致。我们的结果可以解决谷电子学的关键挑战，并证明范德华磁体在磁光电子应用中具有广阔前景。
