Closing the surface bandgap in thin Bi2Se3/Graphene heterostructures

Jimin Chae, Seoung Hun Kang, Sang Han Park, Hanbum Park, Kwangsik Jeong, Tae Hyeon Kim, Seok Bo Hong, Keun Su Kim, Young Kyun Kwon, Jeong Won Kim, Mann Ho Cho

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Abstract

Topological insulator (TI), a band insulator with topologically protected edge states, is one of the most interesting materials in the field of condensed matter. Bismuth selenide (Bi2Se3) is the most spotlighted three-dimensional TI material; it has a Dirac cone at each top and bottom surface and a relatively wide bandgap. For application, suppression of the bulk effect is crucial, but in ultrathin TI materials, with thicknesses less than 3 QL, the finite size effect works on the linear dispersion of the surface states, so that the surface band has a finite bandgap because of the hybridization between the top and bottom surface states and Rashba splitting, resulting from the structure inversion asymmetry. Here, we studied the gapless top surface Dirac state of strained 3 QL Bi2Se3/graphene heterostructures. A strain caused by the graphene layer reduces the bandgap of surface states, and the band bending resulting from the charge transfer at the Bi2Se3-graphene interface induces localization of surface states to each top and bottom layer to suppress the overlap of the two surface states. In addition, we verified the independent transport channel of the top surface Dirac state in Bi2Se3/graphene heterostructures by measuring the magneto-conductance. Our findings suggest that the strain and the proximity effect in TI/non-TI heterostructures may be feasible ways to engineer the topological surface states beyond the physical and topological thickness limit.

Original languageEnglish
Pages (from-to)3931-3939
Number of pages9
JournalACS Nano
Volume13
Issue number4
DOIs
Publication statusPublished - 2019 Apr 23

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All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

Cite this

Chae, J., Kang, S. H., Park, S. H., Park, H., Jeong, K., Kim, T. H., Hong, S. B., Kim, K. S., Kwon, Y. K., Kim, J. W., & Cho, M. H. (2019). Closing the surface bandgap in thin Bi2Se3/Graphene heterostructures. ACS Nano, 13(4), 3931-3939. https://doi.org/10.1021/acsnano.8b07012