Topological insulators display unique properties, such as the quantum spin Hall effect, because time-reversal symmetry allows charges and spins to propagate along the edge or surface of the topological insulator without scattering1,2,3,4,5,6,7,8,9,10,11,12,13,14. However, the direct manipulation of these edge/surface states is difficult because they are significantly outnumbered by bulk carriers9,15,16. Here, we report experimental evidence for the modulation of these surface states by using a gate voltage to control quantum oscillations in Bi2Te3 nanoribbons. Surface conduction can be significantly enhanced by the gate voltage, with the mobility and Fermi velocity reaching values as high as ~5,800 cm2 V−1 s−1 and ~3.7 × 105 m s−1, respectively, with up to ~51% of the total conductance being due to the surface states. We also report the first observation of h/2e periodic oscillations, suggesting the presence of time-reversed paths with the same relative zero phase at the interference point16. The high surface conduction and ability to manipulate the surface states demonstrated here could lead to new applications in nanoelectronics and spintronics.
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The authors thank the Focus Center Research Program-Center on Functional Engineered Nano Architectonics (FENA), Defense Advanced Research Projects Agency (DARPA) and the Australia Research Council (DP0984755, DP0985084) for their financial support. K.L.W. thanks Jeff Rogers (DARPA) and Betsy Weitzman (FENA). Y.W. thanks the Queensland International Fellowship. F.X. acknowledges helpful discussions with Siguang Ma, Yabin Fan and Pramey Upadhyaya (UCLA) and Wei Peng (UC Riverside).
The authors declare no competing financial interests.
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Xiu, F., He, L., Wang, Y. et al. Manipulating surface states in topological insulator nanoribbons. Nature Nanotech 6, 216–221 (2011). https://doi.org/10.1038/nnano.2011.19