Abstract
A topological insulator1,2,3,4,5,6,7,8,9 is a new state of quantum matter that is characterized by a finite energy gap in the bulk and gapless modes flowing along the boundaries that are robust against disorder scattering. The topological protection of the surface state could be useful for both low-power electronics10 and error-tolerant quantum computing11,12. For a thin slab of three-dimensional topological insulator, the boundary modes from the opposite surfaces may be coupled by quantum tunnelling, so that a small, thickness-dependent gap is opened up13,14,15. Here we report such results from angle-resolved photoemission spectroscopy on Bi2Se3 films of various thicknesses grown by molecular beam epitaxy. The energy gap opening is clearly seen when the thickness is below six quintuple layers. The gapped surface states also exhibit sizeable Rashba-type spin–orbit splitting because of the substrate-induced potential difference between the two surfaces. The tunable gap and the spin–orbit coupling make these topological thin films ideal for electronic and spintronic device applications.
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12 August 2010
On the first page of the PDF and printed versions of this Letter originally published, the full list of authors and their affiliations should have been included. This has now been corrected on the PDF version of the Letter.
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Acknowledgements
This work was supported by the National Science Foundation and Ministry of Science and Technology of China and RGC of Hong Kong, China under grant No. HKU 7037/08P. X-L.Q., S-C.Z. and Q.N. are supported by the Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under contracts DE-AC02-76SF00515 and DE-FG03-02ER45958.
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K.H., S-Q.S., X-C.M. and Q-K.X. conceived and designed the experiments. Y.Z., K.H. and C-Z.C. carried out MBE growth and ARPES measurements. C-L.S. carried out substrate preparation and STM observation. L-L.W., X.C., J-F.J., X-C.M. and Q-K.X. assisted in the experiments. W-Y.S. and S-Q.S. carried out the theoretical analyses and data interpretations. Q.N., Z.F., X.D., X-L.Q. and S-C.Z. assisted in the theoretical analyses. Y.Z., K.H., S-Q.S., S-C.Z. and Q-K.X. prepared the manuscript.
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Zhang, Y., He, K., Chang, CZ. et al. Crossover of the three-dimensional topological insulator Bi2Se3 to the two-dimensional limit. Nature Phys 6, 584–588 (2010). https://doi.org/10.1038/nphys1689
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DOI: https://doi.org/10.1038/nphys1689
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