Opto-valleytronics in the 2D van der Waals heterostructure
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Opto-valleytronics in the 2D van der Waals heterostructure Abdullah Rasmita1 and Wei-bo Gao1,2 () 1
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore 2 The Photonics Institute and Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637371, Singapore © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 10 June 2020 / Revised: 31 July 2020 / Accepted: 4 August 2020
ABSTRACT The development of information processing devices with minimum carbon emission is crucial in this information age. One of the approaches to tackle this challenge is by using valleys (local extremum points in the momentum space) to encode the information instead of charges. The valley information in some material such as monolayer transition metal dichalcogenide (TMD) can be controlled by using circularly polarized light. This opens a new field called opto-valleytronics. In this article, we first review the valley physics in monolayer TMD and two-dimensional (2D) heterostructure composed of monolayer TMD and other materials. Such 2D heterostructure has been shown to exhibit interesting phenomena such as interlayer exciton, magnetic proximity effect, and spin-orbit proximity effect, which is beneficial for opto-valleytronics application. We then review some of the optical valley control methods that have been used in the monolayer TMD and the 2D heterostructure. Finally, a summary and outlook of the 2D heterostructure opto-valleytronics are given.
KEYWORDS opto-valleytronics, two-dimensional (2D) heterostructure, interlayer exciton, transition metal dichalcogenide, proximity effect
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Introduction
As the demand for the information processing capability increases, the current method of the charge-based information encoding may not be sufficient anymore. On the other hand, a more energy-efficient way to process and transfer information is also desirable for minimizing the carbon imprint of the communication and computation devices. Additionally, the charge-based method may not be suitable for more advanced methods of information processing, such as quantum computation and communication. In this regard, encoding information in degrees of freedom other than charge may prove to be beneficial. These include spin and valley degree of freedom. When the latter is used, the topics fall into the field of valleytronics [1]. The valleys refer to the local extremum points in the crystal band structure in the momentum space. The electron in a crystal, as well as the hole and the quasi-particle such as bound electron–hole pair (exciton), can have valley property. Compared to the charge-based electronics devices, the valleytronics devices may be more energy-efficient as pure valley current does not induce Joule heating [2, 3]. In the case of opto-valleytronics, the coupling between the valley information and the optical signal is utilized (see Fig. 1(a)). The optical method is th
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