Anisotropic interlayer exciton in black phosphorus van der Waals heterostructures
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Anisotropic interlayer exciton in black phosphorus van der Waals heterostructures Jintong Li1,2 Received: 13 March 2020 / Accepted: 11 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract We study theoretically the variations of interlayer exciton binding energy caused by the exciton–optical phonons coupling in van der Waals heterostructures composed of doublelayer black phosphorus (BP), where both the longitudinal optical phonon modes and the surface optical phonon modes induced by the inserted h-BN layer are taken into account. We find that the strength of exciton–phonon coupling depends on the anisotropy of the effective mass of interlayer exciton, which plays a crucial rule in adjusting the binding energies of interlayer excitons. Moreover, the modulation effects of interlayer distance between two layers as well as the internal distance between BP layer and the inserted h-BN layer on the binding energies are analyzed quantitatively. These results provide theoretical insight when modulating interlayer excitons in two-dimensional van der Waals heterostructures in experiments. Keywords Black phosphorus · Van der Waals heterostructure · Exciton binding energy
1 Introduction In the past decades, two-dimensional van der Waals heterostructures (VDWHS) by stacking different kinds of atomic layered materials, with amounts of special properties, have aroused considerable attention. Among them, black phosphorus (BP) stands out because of its obvious anisotropy along the zigzag and armchair directions, such as the effective mass of carriers, thermal conductivity and mobility (Ankit et al. 2015; Tran et al. 2014; Chao et al. 2016; Liu et al. 2014; Mogulkoc et al. 2016; Qiao et al. 2014; Rudenko et al. 2016; Wang et al. 2016). These anisotropy make BP VDWHS an ideal platform for fabricating specific electronic devices (Fang et al. 2014; Withers et al. 2015; Butov 2017). On the other hand, interlayer excitons in these VDWHS, in which an electron and a hole are confined in spatially separated double layers, owing to its potential applications in exciton devices, has also attracted an increasing number of interests in recent years (Jose et al. 2016; Shi et al. 2018; Pereira et al. 2015; Sun et al. 2006; Tsuji et al. 2002; High et al. 2007). Nevertheless, most studies * Jintong Li [email protected] 1
The Bullis School, Potomac, MD, USA
2
National Graphene Research and Development Center, Springfield, VA, USA
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regarding interlayer excitons carried out in these VDWHS were based on two-dimensional transition metal dichalcogenides, while the corresponding researches in BP VDWHS are few until now. In fact, the modulation of exciton binding energy in double BP layers has been studied in several papers (Gomez et al. 2014; Tran et al. 2015; Berman et al. 2017; Zhang et al. 2018; Chen et al. 2018) in recent years. Since the binding energy plays a key role in determining the properties of interlayer exciton. Zhang et al. (2018) reporte
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