Valley-polarized exciton currents in a van der waals heterostructure

ABSTRACT Valleytronics is an appealing alternative to conventional charge-based electronics that aims at encoding data in the valley degree of freedom, that is, the information as to which

extreme of the conduction or valence band carriers are occupying. The ability to create and control valley currents in solid-state devices could therefore enable new paradigms for

information processing. Transition metal dichalcogenides (TMDCs) are a promising platform for valleytronics due to the presence of two inequivalent valleys with spin–valley locking1 and a

direct bandgap2,3, which allows optical initialization and readout of the valley state4,5. Recent progress on the control of interlayer excitons in these materials6,7,8 could offer an

effective way to realize optoelectronic devices based on the valley degree of freedom. Here, we show the generation and transport over mesoscopic distances of valley-polarized excitons in a

device based on a type-II TMDC heterostructure. Engineering of the interlayer coupling results in enhanced diffusion of valley-polarized excitons, which can be controlled and switched

electrically. Furthermore, using electrostatic traps, we can increase the exciton concentration by an order of magnitude, reaching densities in the order of 1012 cm−2, opening the route to

achieving a coherent quantum state of valley-polarized excitons via Bose–Einstein condensation. Access through your institution Buy or subscribe This is a preview of subscription content,

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institutional subscriptions * Read our FAQs * Contact customer support SIMILAR CONTENT BEING VIEWED BY OTHERS MAGNETIC-GATEABLE VALLEY EXCITON EMISSION Article Open access 07 July 2020

CONCEPTS OF THE HALF-VALLEY-METAL AND QUANTUM ANOMALOUS VALLEY HALL EFFECT Article Open access 21 August 2020 ROOM-TEMPERATURE VALLEYTRONIC TRANSISTOR Article 20 July 2020 DATA AVAILABILITY

The data that support the findings of this study are available from the corresponding author on reasonable request. REFERENCES * Xiao, D., Liu, G.-B., Feng, W., Xu, X. & Yao, W. Coupled

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671–675 (2012). Article  CAS  Google Scholar  Download references ACKNOWLEDGEMENTS We are grateful to J.F. Gonzalez Marin for useful discussions. We acknowledge the help of Z. Benes (EPFL

Center of MicroNanoTechnology (CMI)) with electron-beam lithography. D.U., A.C., A.A. and A.K. acknowledge support by the Swiss National Science Foundation (grant no. 153298), H2020 European

Research Council (ERC, grant no. 682332) and Marie Curie-Sklodowska-Curie Actions (COFUND grant no. 665667). A.K. acknowledges funding from the European Union’s Horizon H2020 Future and

Emerging Technologies under grant no. 696656 (Graphene Flagship). K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan and JSPS KAKENHI

grants nos. JP15K21722 and JP25106006. AUTHOR INFORMATION Author notes * These authors contributed equally: Dmitrii Unuchek, Alberto Ciarrocchi. AUTHORS AND AFFILIATIONS * Electrical

Engineering Institute, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland Dmitrii Unuchek, Alberto Ciarrocchi, Ahmet Avsar, Zhe Sun & Andras Kis * Institute of

Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland Dmitrii Unuchek, Alberto Ciarrocchi, Ahmet Avsar, Zhe Sun & Andras Kis *

National Institute for Materials Science, Tsukuba, Japan Kenji Watanabe & Takashi Taniguchi Authors * Dmitrii Unuchek View author publications You can also search for this author

inPubMed Google Scholar * Alberto Ciarrocchi View author publications You can also search for this author inPubMed Google Scholar * Ahmet Avsar View author publications You can also search

for this author inPubMed Google Scholar * Zhe Sun View author publications You can also search for this author inPubMed Google Scholar * Kenji Watanabe View author publications You can also

search for this author inPubMed Google Scholar * Takashi Taniguchi View author publications You can also search for this author inPubMed Google Scholar * Andras Kis View author publications

You can also search for this author inPubMed Google Scholar CONTRIBUTIONS A.K. initiated and supervised the project. A.C. fabricated the devices. D.U. performed optical measurements with

assistance from A.C. A.C. and D.U. analysed the data. Z.S., A.C. and D.U. performed SHG measurements. K.W. and T.T. grew the hBN crystals. A.C., D.U., A.A. and A.K. wrote the manuscript,

with input from all authors. CORRESPONDING AUTHOR Correspondence to Andras Kis. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no competing interests. ADDITIONAL INFORMATION

PEER REVIEW INFORMATION _Nature Nanotechnology_ thanks Min-Kyu Joo and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. PUBLISHER’S NOTE Springer

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refs. 1–5. RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Unuchek, D., Ciarrocchi, A., Avsar, A. _et al._ Valley-polarized exciton currents in a van

der Waals heterostructure. _Nat. Nanotechnol._ 14, 1104–1109 (2019). https://doi.org/10.1038/s41565-019-0559-y Download citation * Received: 03 June 2019 * Accepted: 16 September 2019 *

Published: 21 October 2019 * Issue Date: December 2019 * DOI: https://doi.org/10.1038/s41565-019-0559-y SHARE THIS ARTICLE Anyone you share the following link with will be able to read this

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