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Electrical control of charged carriers and excitons in atomically thin materials

Abstract

Electrical confinement and manipulation of charge carriers in semiconducting nanostructures are essential for realizing functional quantum electronic devices1,2,3. The unique band structure4,5,6,7 of atomically thin transition metal dichalcogenides (TMDs) offers a new route towards realizing novel 2D quantum electronic devices, such as valleytronic devices and valley–spin qubits8. 2D TMDs also provide a platform for novel quantum optoelectronic devices9,10,11 due to their large exciton binding energy12,13. However, controlled confinement and manipulation of electronic and excitonic excitations in TMD nanostructures have been technically challenging due to the prevailing disorder in the material, preventing accurate experimental control of local confinement and tunnel couplings14,15,16. Here we demonstrate a novel method for creating high-quality heterostructures composed of atomically thin materials that allows for efficient electrical control of excitations. Specifically, we demonstrate quantum transport in the gate-defined, quantum-confined region, observing spin–valley locked quantized conductance in quantum point contacts. We also realize gate-controlled Coulomb blockade associated with confinement of electrons and demonstrate electrical control over charged excitons with tunable local confinement potentials and tunnel couplings. Our work provides a basis for novel quantum opto-electronic devices based on manipulation of charged carriers and excitons.

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Fig. 1: Semiconducting van der Waals heterostructure with mesoscopic backgates.
Fig. 2: Conductance quantization via quantum point contact.
Fig. 3: Quantum confinement of charge carriers.
Fig. 4: Optoelectronic transport in gate-defined MoSe2 nanostructures.
Fig. 5: Gate-defined confinement of charged excitons.

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Acknowledgements

We thank J. Waissman and E. Lee for helpful discussions. The major experimental work was supported by AFOSR (grant FA9550-14-1-0268), DoD Vannevar Bush Faculty Fellowship (grant N00014-16-1-2825), and Samsung Electronics. K.W. acknowledges support from ARO MURI (W911NF-14-1-0247). P.K. acknowledges partial support from ONR MURI (grant N00014-15-1-2761) and the FAME Center. H.P. and M.D.L. acknowledge partial support from AFOSR MURI (FA9550-17-1-0002), NSF (PHY-1506284), and NSF CUA (PHY-1125846). K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan and JSPS KAKENHI grant numbers JP26248061, JP15K21722 and JP25106006. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1157490 and the State of Florida. Nanofabrication was performed at the Center for Nanoscale Systems at Harvard, supported in part by an NSF NNIN award ECS-00335765.

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K.W. performed the experiments and analysed the data. K.D.G., L.J., A.S., A.H., Y.Z. and G.S. performed optical measurements, K.W. and L.J. fabricated devices, K.W. and P.K. conceived the electron transport experiment. K.W., K.D.G., M.L., H.P. and P.K. conceived the optoelectronic experiment. K.W. and T.T. provided hBN crystals.

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Correspondence to Philip Kim.

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Supplementary Figs. 1–3 and Supplementary References.

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Wang, K., De Greve, K., Jauregui, L.A. et al. Electrical control of charged carriers and excitons in atomically thin materials. Nature Nanotech 13, 128–132 (2018). https://doi.org/10.1038/s41565-017-0030-x

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