Inverse Funnel Effect of Excitons in Strained Black Phosphorus

Pablo San-jose, Vincenzo Parente, Francisco Guinea, Rafael Roldán, Elsa Prada

    Research output: Contribution to journalArticlepeer-review

    Abstract

    We study the effects of strain on the properties and dynamics of Wannier excitons in monolayer (phosphorene) and few-layer black phosphorus (BP), a promising two-dimensional material for optoelectronic applications due to its high mobility, mechanical strength, and strain-tunable direct band gap. We compare the results to the case of molybdenum disulphide (MoS2) monolayers. We find that the so-called funnel effect, i.e., the possibility of controlling exciton motion by means of inhomogeneous strains, is much stronger in few-layer BP than in MoS2 monolayers and, crucially, is of opposite sign. Instead of excitons accumulating isotropically around regions of high tensile strain like in MoS2, excitons in BP are pushed away from said regions. This inverse funnel effect is moreover highly anisotropic, with much larger funnel distances along the armchair crystallographic direction, leading to a directional focusing of exciton flow. A strong inverse funnel effect could enable simpler designs of funnel solar cells and offer new possibilities for the manipulation and harvesting of light.
    Original languageEnglish
    Article number031046
    JournalPhysical Review X
    Volume6
    Issue number3
    Early online date27 Sept 2016
    DOIs
    Publication statusPublished - 27 Sept 2016

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