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Spin–layer locking of interlayer excitons trapped in moiré potentials

Abstract

Van der Waals heterostructures offer attractive opportunities to design quantum materials. For instance, transition metal dichalcogenides (TMDs) possess three quantum degrees of freedom: spin, valley index and layer index. Furthermore, twisted TMD heterobilayers can form moiré patterns that modulate the electronic band structure according to the atomic registry, leading to spatial confinement of interlayer excitons (IXs). Here we report the observation of spin–layer locking of IXs trapped in moiré potentials formed in a heterostructure of bilayer 2H-MoSe2 and monolayer WSe2. The phenomenon of locked electron spin and layer index leads to two quantum-confined IX species with distinct spin–layer–valley configurations. Furthermore, we observe that the atomic registries of the moiré trapping sites in the three layers are intrinsically locked together due to the 2H-type stacking characteristic of bilayer TMDs. These results identify the layer index as a useful degree of freedom to engineer tunable few-level quantum systems in two-dimensional heterostructures.

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Fig. 1: Spin–layer locking of moiré-trapped IXs in a van der Waals heterostructure.
Fig. 2: Optical spectroscopy properties of spin–layer-locked IXs trapped in moiré potentials.
Fig. 3: Magneto-optic properties of spin–layer-locked IXs trapped in moiré potentials.
Fig. 4: Optical selection rules of spin–layer-locked IXs trapped in moiré potentials.

Data availability

Data described in this paper and presented in the Supplementary Information are available online at https://researchportal.hw.ac.uk/en/persons/brian-d-gerardot/datasets/.

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Acknowledgements

We thank J. J. Finley, K. Müller, M. Kremser and A. Högele for discussions. This work is supported by the EPSRC (grant no. EP/P029892/1 and EP/S000550/1), the ERC (grant no. 725920) and the EU Horizon 2020 research and innovation programme under grant agreement no. 820423. A.M.-S. acknowledges the Juan de la Cierva programme (grant IJCI-2015-25799; MINECO, Spain) and the Marie-Curie-COFUND programme Nano TRAIN For Growth II (grant agreement 713640). The computations were performed on the Tirant III cluster of the Servei d’Informàtica of the University of Valencia (project vlc82). Growth of hBN crystals by K.W. and T.T. was supported by the Elemental Strategy Initiative conducted by the MEXT, Japan and the CREST (JPMJCR15F3). B.D.G. is supported by a Wolfson Merit Award from the Royal Society and a Chair in Emerging Technology from the Royal Academy of Engineering.

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B.D.G. conceived and supervised the project. H.B. fabricated the samples. K.W. and T.T. supplied the hBN crystals. M.B.-G. and H.B. performed the experiments, assisted by A.C., C.B. and D.W.; M.B.-G. analysed the data, assisted by E.S. and B.D.G.; A.M.-S. performed the ab initio calculations. M.B.-G. and B.D.G. cowrote the paper with input from all authors. M.B.-G. and H.B. contributed equally to this work.

Corresponding authors

Correspondence to Mauro Brotons-Gisbert or Hyeonjun Baek or Brian D. Gerardot.

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Supplementary Information

Supplementary Notes 1-8 and Figs. 1-10.

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Brotons-Gisbert, M., Baek, H., Molina-Sánchez, A. et al. Spin–layer locking of interlayer excitons trapped in moiré potentials. Nat. Mater. 19, 630–636 (2020). https://doi.org/10.1038/s41563-020-0687-7

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