Electron interaction-driven insulating ground state in Bi2Se3 topological insulators in the two dimensional limit

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We report a transport study of ultrathin Bi2Se3 topological insulators with thickness from one quintuple layer to six quintuple layers grown by molecular beam epitaxy.

• At low temperatures, the film resistance increases logarithmically with decreasing temperature, revealing an insulating ground state.
• The sharp increase of resistance with magnetic field, however, indicates the existence of weak antilocalization, which should reduce the resistance as temperature decreases.
• We show that these apparently contradictory behaviors can be understood by considering the electron interaction effect, which plays a crucial role in determining the electronic ground state of topological insulators in the two dimensional limit.