Valley-polarized exciton currents in a van der Waals heterostructure.,Nature Nanotechnology

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Valley-polarized exciton currents in a van der Waals heterostructure.
Nature Nanotechnology ( IF 38.1 ) Pub Date : 2019-10-21 , DOI: 10.1038/s41565-019-0559-y
Dmitrii Unuchek _{1,

2} , Alberto Ciarrocchi _{1,

2} , Ahmet Avsar _{1,

2} , Zhe Sun _{1,

2} , Kenji Watanabe ₃ , Takashi Taniguchi ₃ , Andras Kis _{1,

2}

Affiliation

Valleytronics is an appealing alternative to conventional charge-based electronics that aims at encoding data in the valley degree of freedom, that is, the information as to which extreme of the conduction or valence band carriers are occupying. The ability to create and control valley currents in solid-state devices could therefore enable new paradigms for information processing. Transition metal dichalcogenides (TMDCs) are a promising platform for valleytronics due to the presence of two inequivalent valleys with spin-valley locking1 and a direct bandgap2,3, which allows optical initialization and readout of the valley state4,5. Recent progress on the control of interlayer excitons in these materials6-8 could offer an effective way to realize optoelectronic devices based on the valley degree of freedom. Here, we show the generation and transport over mesoscopic distances of valley-polarized excitons in a device based on a type-II TMDC heterostructure. Engineering of the interlayer coupling results in enhanced diffusion of valley-polarized excitons, which can be controlled and switched electrically. Furthermore, using electrostatic traps, we can increase the exciton concentration by an order of magnitude, reaching densities in the order of 1012 cm-2, opening the route to achieving a coherent quantum state of valley-polarized excitons via Bose-Einstein condensation.

中文翻译：

范德华异质结构中的谷极化激子电流。

Valleytronics 是传统基于电荷的电子器件的一种有吸引力的替代方案，旨在以谷自由度编码数据，即关于导带或价带载流子占据哪个极端的信息。因此，在固态器件中产生和控制谷电流的能力可以为信息处理带来新的范例。过渡金属二硫化物 (TMDC) 是谷电子学的一个有前途的平台，因为它存在两个具有自旋谷锁定 1 的不等价谷和直接带隙 2,3，允许光学初始化和谷态读出 4,5。这些材料中层间激子控制的最新进展6-8可以为实现基于谷自由度的光电器件提供有效的方法。在这里，我们展示了基于 II 型 TMDC 异质结构的器件中谷偏振激子在介观距离上的产生和传输。层间耦合工程增强了谷极化激子的扩散，可以通过电控制和切换。此外，利用静电陷阱，我们可以将激子浓度提高一个数量级，达到1012 cm-2数量级的密度，为通过玻色-爱因斯坦凝聚实现谷偏振激子的相干量子态开辟了道路。

更新日期：2019-10-21

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