Abstract
The surface state of a topological insulator always has a weak antilocalization (WAL), and the bulk state would theoretically have a weak localization (WL). Although the WAL topological surface state has been observed, the WL bulk state has never been demonstrated by experiments. Using the Sn-doping Bi${}_{2}$Te${}_{3}$ polycrystalline topological insulator films and the magnetotransport characteristic analysis, we directly observed the WL effect from the bulk state. The experimental data suggested that an inflection from WAL to WL indeed takes place in the parallel magnetoresistance (MR) curve of the low-doped film with increasing the magnetic field, and the inversion phenomenon from a positive to a negative MR cusp at low fields driven by the temperature was observed in the parallel MR trace of the high-doped sample. Observations of the WL bulk state actually open a path toward magnetic device application of a topological insulator, and the polycrystalline topological insulator films provide an attractive material platform to explore the novel effects of topological insulators.
Published Version
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