Valley-selective circular dichroism of monolayer molybdenum disulphide.
Valley-selective circular dichroism of monolayer molybdenum disulphide.
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单层二硫化钼的谷选择性圆二色性
DOI：
10.1038/ncomms1882
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发表时间：
2012-06-06
影响因子：
16.6
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中科院分区：
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二维蜂窝晶格在k空间的电子结构中含有一对不等效谷，位于六方布里渊区K±的顶点附近。特别吸引人的是利用这种新兴的自由电荷载体，也就是所谓的电子电子技术。山谷的物理模拟了自旋的物理，并将使类似于自旋电子学的器件成为可能，如山谷过滤器和阀，以及光电子霍尔器件，所有这些都非常有希望成为下一代电子学。关键的挑战在于实现谷极化，在二维蜂窝结构中令人信服的演示仍然是回避的。在这里，我们用第一性原理计算表明，单层二硫化钼是一种理想的电谷电子材料，它的谷极化可以通过它独特的对称性引起的谷选择性圆二色性来实现。我们还通过测量单层二硫化钼的圆偏振光致发光提供了实验证据，显示出高达50%的偏振。单层过渡金属二卤化物二硫化钼因其独特的电子性质最近引起了人们的关注。CaO和他的同事提出的数值证据表明，圆偏振光可以优先激发该系统能带结构中的单个谷。
A two-dimensional honeycomb lattice harbours a pair of inequivalent valleys in the k-space electronic structure, in the vicinities of the vertices of a hexagonal Brillouin zone, K±. It is particularly appealing to exploit this emergent degree of freedom of charge carriers, in what is termed 'valleytronics'. The physics of valleys mimics that of spin, and will make possible devices, analogous to spintronics, such as valley filter and valve, and optoelectronic Hall devices, all very promising for next-generation electronics. The key challenge lies with achieving valley polarization, of which a convincing demonstration in a two-dimensional honeycomb structure remains evasive. Here we show, using first principles calculations, that monolayer molybdenum disulphide is an ideal material for valleytronics, for which valley polarization is achievable via valley-selective circular dichroism arising from its unique symmetry. We also provide experimental evidence by measuring the circularly polarized photoluminescence on monolayer molybdenum disulphide, which shows up to 50% polarization. The monolayer transition-metal dichalcogenide molybdenum disulphide has recently attracted attention owing to its distinctive electronic properties. Cao and co-workers present numerical evidence suggesting that circularly polarized light can preferentially excite a single valley in the band structure of this system.