Nonideal topological insulator (TI) films in which the bulk states are not insulating due to unintentional doping exhibit strong surface-bulk coupling. Such surface-bulk coupling can further induce intersurface coupling that affects the electrical conductivity of the TI films through a quantum interference effect known as weak antilocalization. Increased understanding and control of intersurface coupling is therefore crucial for the use of TI-based quantum devices. In this report on the transport properties of doped Bi2Se3 films under perpendicular and parallel magnetic fields, we observe a crossover between coupled and decoupled surface channels that is mediated by intentional disorder controlled by a post-annealing process. The intentional disorder causes the surface state carriers to rapidly lose their quantum phase and coherence, and as a result, more disordered Bi2Se3 films exhibit a shorter penetration depth of the surface state into the bulk states and weaker intersurface coupling, even though stronger surface-bulk coupling is expected. In previous studies, the role of disorder has generally been considered by determining its effect on surface-bulk scattering, but our results indicate that the role of disorder must be considered as a source of decoherence.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (Grant No. 2018R1A2A1A05023214) and by Samsung Research Funding Center of Samsung Electronics under Project No. SRFC-MA1502-01 and by the Korea Research Institute of Standards and Science (KRISS) under the Metrology Research Center project. The authors would like to thank Hee-Suk Chung at the Korea Basic Science Institute for technical assistance with STEM and Byeong-Gyu Park at the Pohang Accelerator Laboratory for technical assistance with ARPES.
© 2018 American Physical Society.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics