Tunable surface conductivity in Bi2Se3 revealed in diffusive electron transport

We demonstrate that the weak antilocalization effect can serve as a convenient method for detecting decoupled surface transport in topological insulator thin films. In the regime where a bulk Fermi surface coexists with the surface states, the low-field magnetoconductivity is well described by the Hikami-Larkin-Nagaoka equation for single-component transport of noninteracting electrons. When the electron density is lowered, the magnetotransport behavior deviates from the single-component description and strong evidence is found for independent conducting channels at or near the bottom and top surfaces. The magnetic-field-dependent part of corrections to conductivity due to Zeeman energy is shown to be negligible for the fields relevant to the weak antilocalization despite considerable electron-electron interaction effects on the temperature dependence of the conductivity.