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キーワード:
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要旨:
Topological insulators (TIs) represent a new quantum state of matter
characterized by robust gapless states inside the insulating bulk gap.
The metallic edge states of a two-dimensional (2D) TI, known as the
quantum spin Hall (QSH) effect, are immune to backscattering and carry
fully spin-polarized dissipationless currents. However, existing 2D TIs
realized in HgTe and InAs/GaSb suffer from small bulk gaps (<10 meV)
well below room temperature, thus limiting their application in
electronic and spintronic devices. Here, we report a new 2D TI
comprising a graphene layer sandwiched between two Bi2Se3 slabs that
exhibits a large intrinsic bulk band gap of 30-50 meV, making it viable
for room-temperature applications. Distinct from previous strategies for
enhancing the intrinsic spin-orbit coupling effect of the graphene
lattice, the present graphene-based TI operates on a new mechanism of
strong inversion between graphene Dirac bands and Bi2Se3 conduction
bands. Strain engineering leads to effective control and substantial
enhancement of the bulk gap. Recently reported synthesis of smooth
graphene/Bi2Se3 interfaces demonstrates the feasibility of experimental
realization of this new 2D TI structure, which holds great promise for
nanoscale device applications.
