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Quantum dots with single-atom precision

Nature Nanotechnology volume 9, pages 505–508 (2014)Cite this article

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Abstract

Quantum dots are often called artificial atoms because, like real atoms, they confine electrons to quantized states with discrete energies. However, although real atoms are identical, most quantum dots comprise hundreds or thousands of atoms, with inevitable variations in size and shape and, consequently, unavoidable variability in their wavefunctions and energies. Electrostatic gates can be used to mitigate these variations by adjusting the electron energy levels1,2,3, but the more ambitious goal of creating quantum dots with intrinsically digital fidelity by eliminating statistical variations in their size, shape and arrangement remains elusive4,5,6,7,8,9. We used a scanning tunnelling microscope to create quantum dots with identical, deterministic sizes. By using the lattice of a reconstructed semiconductor surface to fix the position of each atom, we controlled the shape and location of the dots with effectively zero error. This allowed us to construct quantum dot molecules whose coupling has no intrinsic variation but could nonetheless be tuned with arbitrary precision over a wide range. Digital fidelity opens the door to quantum dot architectures free of intrinsic broadening—an important goal for technologies from nanophotonics10 to quantum information processing11,12 as well as for fundamental studies of confined electrons13,14,15,16,17.

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Figure 1: Quantized states of a digital quantum dot in which electrons are confined by a chain of ionized adatoms.
Figure 2: Theoretical description of pristine and quantized surface states.
Figure 3: Antibonding states of two weakly coupled adatom chains forming a digital quantum dot molecule.
Figure 4: Protected degeneracy in a digital triple dot.

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Acknowledgements

The authors thank C.S. Hellberg, Al. L. Efros and E.I. Rashba for discussions. This work was supported by the German Research Foundation (FO 362/4-1) and the Office of Naval Research through the Naval Research Laboratory's Basic Research Program. Computations were performed at the DoD Major Shared Resource Center at AFRL.

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Authors and Affiliations

  1. Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, Berlin, 10117, Germany

    Stefan Fölsch, Jesús Martínez-Blanco & Jianshu Yang

  2. NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa, 243-0198, Japan

    Kiyoshi Kanisawa

  3. Center for Computational Materials Science, Naval Research Laboratory, Washington, 20375, DC, USA

    Steven C. Erwin

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  1. Stefan Fölsch
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  2. Jesús Martínez-Blanco
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  3. Jianshu Yang
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  4. Kiyoshi Kanisawa
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  5. Steven C. Erwin
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Contributions

J.Y., J.M-B., and S.F. performed the experiments. S.F. carried out the experimental data analysis. K.K. performed the MBE growth of the samples and participated in discussions of the results. S.C.E. performed the DFT calculations and tight-binding theoretical modelling. S.F. and S.C.E. wrote the manuscript.

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Correspondence to Stefan Fölsch or Steven C. Erwin.

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The authors declare no competing financial interests.

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Fölsch, S., Martínez-Blanco, J., Yang, J. et al. Quantum dots with single-atom precision. Nature Nanotech 9, 505–508 (2014). https://doi.org/10.1038/nnano.2014.129

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