22 February 2018 Optical spectroscopy of interlayer excitons in TMDC heterostructures: exciton dynamics, interactions, and giant valley-selective magnetic splitting
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Abstract
Two-dimensional transition-metal dichalcogenides (TMDCs) have recently emerged as a promising class of materials. A fascinating aspect of these atomically thin crystals is the possibility of combining different TMDCs into heterostructures. For several TMDC combinations, a staggered band alignment occurs, so that optically excited electron-hole pairs are spatially separated into different layers and form interlayer excitons (IEX). Here, we report on time-resolved, low-temperature photoluminescence (PL) of these IEX in a MoSe2-WSe2 heterostructure. In the time-resolved measurements, we observe indications of IEX diffusion in an inhomogeneous potential landscape. Excitation-density-dependent measurements reveal a dipolar, repulsive exciton-exciton interaction. PL measurements in applied magnetic fields show a giant valley-selective splitting of the IEX luminescence, with an effective g factor of about -15. This large value stems from the alignment of K+ and K- valleys of the constituent monolayers in our heterostructure, making intervalley transitions optically bright, so that contributions to the field-induced splitting arising from electron and hole valley magnetic moments add up. This giant splitting enables us to generate a near-unity valley polarization of interlayer excitons even under linearly polarized excitation by applying sufficiently large magnetic fields.
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Philipp Nagler, Fabian Mooshammer, Mariana V. Ballotin, Anatolie A. Mitioglu, Gerd Plechinger, Sebastian Meier, Nicola Paradiso, Christoph Strunk, Rupert Huber, Alexey Chernikov, Peter C. M. Christianen, Christian Schüller, Tobias Korn, "Optical spectroscopy of interlayer excitons in TMDC heterostructures: exciton dynamics, interactions, and giant valley-selective magnetic splitting", Proc. SPIE 10530, Ultrafast Phenomena and Nanophotonics XXII, 1053015 (22 February 2018); doi: 10.1117/12.2286276; https://doi.org/10.1117/12.2286276
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