Dielectric disorder in two-dimensional materials

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Abstract

Understanding and controlling disorder is key to nanotechnology and materials science. Traditionally, disorder is attributed to local fluctuations of inherent material properties such as chemical and structural composition, doping or strain. Here, we present a fundamentally new source of disorder in nanoscale systems that is based entirely on the local changes of the Coulomb interaction due to fluctuations of the external dielectric environment. Using two-dimensional semiconductors as prototypes, we experimentally monitor dielectric disorder by probing the statistics and correlations of the exciton resonances, and theoretically analyse the influence of external screening and phonon scattering. Even moderate fluctuations of the dielectric environment are shown to induce large variations of the bandgap and exciton binding energies up to the 100 meV range, often making it a dominant source of inhomogeneities. As a consequence, dielectric disorder has strong implications for both the optical and transport properties of nanoscale materials and their heterostructures.

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Fig. 1: Dielectric disorder from spatial fluctuations of the dielectric screening.
Fig. 2: Low-temperature exciton linewidth statistics.
Fig. 3: Correlation analysis and spatially resolved exciton spectroscopy.
Fig. 4: Impact of dielectric disorder on optics and exciton transport in heterostructures.

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All relevant data are available from the authors upon reasonable request.

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Acknowledgements

The authors thank M.M. Glazov and D.R. Reichman for interesting and helpful discussions. The authors thank all our colleagues who have contributed to individual sample preparation: G. Arefe, H.M. Hill, J. Hone, P. Nagler, T. Korn, A.F. Rigosi, J. Yu, A. van der Zande and X. Zhang. Financial support by the DFG via Emmy Noether grant no. CH 1672/1-1 and Collaborative Research Center SFB 1277 (B05) is acknowledged. This research was supported by the AMOS programme at the SLAC National Accelerator Laboratory within the Chemical Sciences Geosciences and Biosciences Division for data analysis, by the National Science Foundation under grant no. DMR-1708457 for the fabrication of samples on h-BN, and by the Gordon and Betty Moore Foundation’s EPiQS programme through grant no. GBMF4545 for spectroscopic measurements. A.R. acknowledges funding through the Heising-Simons Junior Fellowship within the Kavli Energy NanoScience Institute at the University of California, Berkeley. L.W. acknowledges support by the Alexander von Humboldt Foundation. This work was partially supported by the US–Israel Binational Science Foundation grant no. BSF-2016362 (Y.C. and T.C.B.). The Flatiron Institute is a division of the Simons Foundation. The project has also received funding from the Swedish Research Council (VR) and the European Union’s Horizon 2020 research and innovation programme under grant no. 785219 (Graphene Flagship). Growth of hBN crystals was supported by the Elemental Strategy Initiative conducted by the MEXT, Japan and the CREST (JPMJCR15F3), JST.

Author information

A.C. and A.R. conceived the idea, with L.W., T.C.B and T.F.H. providing additional input. A.R., L.W., J.Z., J.D.Z., M.K. and A.C. prepared the samples, carried out the experiments and analysed the data. Y.C. and T.C.B. performed theoretical calculations of the dielectric effects. S.B. and E.M. performed calculations of the exciton–phonon scattering rates. T.T. and K.W. provided high-quality hBN crystals. A.C., A.R. and L.W. wrote the manuscript with input from all authors.

Correspondence to Archana Raja or Alexey Chernikov.

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Supplementary Information

Supplementary Sections 1–10, Supplementary Figs. S1–S15, Supplementary refs. 1–30.

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